diff --git a/bin/pt-config-diff b/bin/pt-config-diff
index 3e40199e..5d648522 100755
--- a/bin/pt-config-diff
+++ b/bin/pt-config-diff
@@ -2641,8 +2641,7 @@ sub _d {
 {
 package ReportFormatter;
 
-use strict;
-use warnings FATAL => 'all';
+use Mo;
 use English qw(-no_match_vars);
 use constant PTDEBUG => $ENV{PTDEBUG} || 0;
 
@@ -2652,40 +2651,102 @@ use POSIX qw(ceil);
 eval { require Term::ReadKey };
 my $have_term = $EVAL_ERROR ? 0 : 1;
 
-sub new {
-   my ( $class, %args ) = @_;
-   my @required_args = qw();
-   foreach my $arg ( @required_args ) {
-      die "I need a $arg argument" unless $args{$arg};
-   }
-   my $self = {
-      underline_header     => 1,
-      line_prefix          => '# ',
-      line_width           => 78,
-      column_spacing       => ' ',
-      extend_right         => 0,
-      truncate_line_mark   => '...',
-      column_errors        => 'warn',
-      truncate_header_side => 'left',
-      strip_whitespace     => 1,
-      %args,              # args above can be overriden, args below cannot
-      n_cols              => 0,
-   };
 
-   if ( ($self->{line_width} || '') eq 'auto' ) {
+has underline_header => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has line_prefix => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '# ' },
+);
+has line_width => (
+   is      => 'ro',
+   isa     => 'Int',
+   default => sub { 78 },
+);
+has column_spacing => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { ' ' },
+);
+has extend_right => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { '' },
+);
+has truncate_line_mark => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '...' },
+);
+has column_errors => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'warn' },
+);
+has truncate_header_side => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'left' },
+);
+has strip_whitespace => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has title => (
+   is        => 'rw',
+   isa       => 'Str',
+   predicate => 'has_title',
+);
+
+
+has n_cols => (
+   is      => 'rw',
+   isa     => 'Int',
+   default => sub { 0 },
+   init_arg => undef,
+);
+
+has cols => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_cols',
+);
+
+has lines => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_lines',
+);
+
+has truncate_headers => (
+   is       => 'rw',
+   isa      => 'Bool',
+   default  => sub { undef },
+   init_arg => undef,
+   clearer  => 'clear_truncate_headers',
+);
+
+sub BUILDARGS {
+   my $class = shift;
+   my $args  = $class->SUPER::BUILDARGS(@_);
+
+   if ( ($args->{line_width} || '') eq 'auto' ) {
       die "Cannot auto-detect line width because the Term::ReadKey module "
          . "is not installed" unless $have_term;
-      ($self->{line_width}) = GetTerminalSize();
+      ($args->{line_width}) = GetTerminalSize();
+      PTDEBUG && _d('Line width:', $args->{line_width});
    }
-   PTDEBUG && _d('Line width:', $self->{line_width});
 
-   return bless $self, $class;
-}
-
-sub set_title {
-   my ( $self, $title ) = @_;
-   $self->{title} = $title;
-   return;
+   return $args;
 }
 
 sub set_columns {
@@ -2701,7 +2762,7 @@ sub set_columns {
       die "Column does not have a name" unless defined $col_name;
 
       if ( $col->{width} ) {
-         $col->{width_pct} = ceil(($col->{width} * 100) / $self->{line_width});
+         $col->{width_pct} = ceil(($col->{width} * 100) / $self->line_width());
          PTDEBUG && _d('col:', $col_name, 'width:', $col->{width}, 'chars =',
             $col->{width_pct}, '%');
       }
@@ -2728,10 +2789,10 @@ sub set_columns {
 
       $col->{right_most} = 1 if $i == $#cols;
 
-      push @{$self->{cols}}, $col;
+      push @{$self->cols}, $col;
    }
 
-   $self->{n_cols} = scalar @cols;
+   $self->n_cols( scalar @cols );
 
    if ( ($used_width || 0) > 100 ) {
       die "Total width_pct for all columns is >100%";
@@ -2741,15 +2802,15 @@ sub set_columns {
       my $wid_per_col = int((100 - $used_width) / scalar @auto_width_cols);
       PTDEBUG && _d('Line width left:', (100-$used_width), '%;',
          'each auto width col:', $wid_per_col, '%');
-      map { $self->{cols}->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
+      map { $self->cols->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
    }
 
-   $min_hdr_wid += ($self->{n_cols} - 1) * length $self->{column_spacing};
+   $min_hdr_wid += ($self->n_cols() - 1) * length $self->column_spacing();
    PTDEBUG && _d('min header width:', $min_hdr_wid);
-   if ( $min_hdr_wid > $self->{line_width} ) {
+   if ( $min_hdr_wid > $self->line_width() ) {
       PTDEBUG && _d('Will truncate headers because min header width',
-         $min_hdr_wid, '> line width', $self->{line_width});
-      $self->{truncate_headers} = 1;
+         $min_hdr_wid, '> line width', $self->line_width());
+      $self->truncate_headers(1);
    }
 
    return;
@@ -2758,14 +2819,14 @@ sub set_columns {
 sub add_line {
    my ( $self, @vals ) = @_;
    my $n_vals = scalar @vals;
-   if ( $n_vals != $self->{n_cols} ) {
+   if ( $n_vals != $self->n_cols() ) {
       $self->_column_error("Number of values $n_vals does not match "
-         . "number of columns $self->{n_cols}");
+         . "number of columns " . $self->n_cols());
    }
    for my $i ( 0..($n_vals-1) ) {
-      my $col   = $self->{cols}->[$i];
+      my $col   = $self->cols->[$i];
       my $val   = defined $vals[$i] ? $vals[$i] : $col->{undef_value};
-      if ( $self->{strip_whitespace} ) {
+      if ( $self->strip_whitespace() ) {
          $val =~ s/^\s+//g;
          $val =~ s/\s+$//;
          $vals[$i] = $val;
@@ -2774,7 +2835,7 @@ sub add_line {
       $col->{min_val} = min($width, ($col->{min_val} || $width));
       $col->{max_val} = max($width, ($col->{max_val} || $width));
    }
-   push @{$self->{lines}}, \@vals;
+   push @{$self->lines}, \@vals;
    return;
 }
 
@@ -2782,26 +2843,28 @@ sub get_report {
    my ( $self, %args ) = @_;
 
    $self->_calculate_column_widths();
-   $self->_truncate_headers() if $self->{truncate_headers};
+   if ( $self->truncate_headers() ) {
+      $self->_truncate_headers();
+   }
    $self->_truncate_line_values(%args);
 
    my @col_fmts = $self->_make_column_formats();
-   my $fmt      = ($self->{line_prefix} || '')
-                . join($self->{column_spacing}, @col_fmts);
+   my $fmt      = $self->line_prefix()
+                . join($self->column_spacing(), @col_fmts);
    PTDEBUG && _d('Format:', $fmt);
 
    (my $hdr_fmt = $fmt) =~ s/%([^-])/%-$1/g;
 
    my @lines;
-   push @lines, sprintf "$self->{line_prefix}$self->{title}" if $self->{title};
+   push @lines, $self->line_prefix() . $self->title() if $self->has_title();
    push @lines, $self->_truncate_line(
-         sprintf($hdr_fmt, map { $_->{name} } @{$self->{cols}}),
+         sprintf($hdr_fmt, map { $_->{name} } @{$self->cols}),
          strip => 1,
          mark  => '',
    );
 
-   if ( $self->{underline_header} ) {
-      my @underlines = map { '=' x $_->{print_width} } @{$self->{cols}};
+   if ( $self->underline_header() ) {
+      my @underlines = map { '=' x $_->{print_width} } @{$self->cols};
       push @lines, $self->_truncate_line(
          sprintf($fmt, map { $_ || '' } @underlines),
          mark  => '',
@@ -2812,19 +2875,23 @@ sub get_report {
       my $vals = $_;
       my $i    = 0;
       my @vals = map {
-            my $val = defined $_ ? $_ : $self->{cols}->[$i++]->{undef_value};
+            my $val = defined $_ ? $_ : $self->cols->[$i++]->{undef_value};
             $val = '' if !defined $val;
             $val =~ s/\n/ /g;
             $val;
       } @$vals;
       my $line = sprintf($fmt, @vals);
-      if ( $self->{extend_right} ) {
+      if ( $self->extend_right() ) {
          $line;
       }
       else {
          $self->_truncate_line($line);
       }
-   } @{$self->{lines}};
+   } @{$self->lines};
+
+   $self->clear_cols();
+   $self->clear_lines();
+   $self->clear_truncate_headers();
 
    return join("\n", @lines) . "\n";
 }
@@ -2832,7 +2899,7 @@ sub get_report {
 sub truncate_value {
    my ( $self, $col, $val, $width, $side ) = @_;
    return $val if length $val <= $width;
-   return $val if $col->{right_most} && $self->{extend_right};
+   return $val if $col->{right_most} && $self->extend_right();
    $side  ||= $col->{truncate_side};
    my $mark = $col->{truncate_mark};
    if ( $side eq 'right' ) {
@@ -2852,8 +2919,8 @@ sub _calculate_column_widths {
    my ( $self ) = @_;
 
    my $extra_space = 0;
-   foreach my $col ( @{$self->{cols}} ) {
-      my $print_width = int($self->{line_width} * ($col->{width_pct} / 100));
+   foreach my $col ( @{$self->cols} ) {
+      my $print_width = int($self->line_width() * ($col->{width_pct} / 100));
 
       PTDEBUG && _d('col:', $col->{name}, 'width pct:', $col->{width_pct},
          'char width:', $print_width,
@@ -2877,7 +2944,7 @@ sub _calculate_column_widths {
 
    PTDEBUG && _d('Extra space:', $extra_space);
    while ( $extra_space-- ) {
-      foreach my $col ( @{$self->{cols}} ) {
+      foreach my $col ( @{$self->cols} ) {
          if (    $col->{auto_width}
               && (    $col->{print_width} < $col->{max_val}
                    || $col->{print_width} < $col->{header_width})
@@ -2892,8 +2959,8 @@ sub _calculate_column_widths {
 
 sub _truncate_headers {
    my ( $self, $col ) = @_;
-   my $side = $self->{truncate_header_side};
-   foreach my $col ( @{$self->{cols}} ) {
+   my $side = $self->truncate_header_side();
+   foreach my $col ( @{$self->cols} ) {
       my $col_name    = $col->{name};
       my $print_width = $col->{print_width};
       next if length $col_name <= $print_width;
@@ -2906,10 +2973,10 @@ sub _truncate_headers {
 
 sub _truncate_line_values {
    my ( $self, %args ) = @_;
-   my $n_vals = $self->{n_cols} - 1;
-   foreach my $vals ( @{$self->{lines}} ) {
+   my $n_vals = $self->n_cols() - 1;
+   foreach my $vals ( @{$self->lines} ) {
       for my $i ( 0..$n_vals ) {
-         my $col   = $self->{cols}->[$i];
+         my $col   = $self->cols->[$i];
          my $val   = defined $vals->[$i] ? $vals->[$i] : $col->{undef_value};
          my $width = length $val;
 
@@ -2935,9 +3002,9 @@ sub _truncate_line_values {
 sub _make_column_formats {
    my ( $self ) = @_;
    my @col_fmts;
-   my $n_cols = $self->{n_cols} - 1;
+   my $n_cols = $self->n_cols() - 1;
    for my $i ( 0..$n_cols ) {
-      my $col = $self->{cols}->[$i];
+      my $col = $self->cols->[$i];
 
       my $width = $col->{right_most} && !$col->{right_justify} ? ''
                 : $col->{print_width};
@@ -2950,12 +3017,12 @@ sub _make_column_formats {
 
 sub _truncate_line {
    my ( $self, $line, %args ) = @_;
-   my $mark = defined $args{mark} ? $args{mark} : $self->{truncate_line_mark};
+   my $mark = defined $args{mark} ? $args{mark} : $self->truncate_line_mark();
    if ( $line ) {
       $line =~ s/\s+$// if $args{strip};
       my $len  = length($line);
-      if ( $len > $self->{line_width} ) {
-         $line  = substr($line, 0, $self->{line_width} - length $mark);
+      if ( $len > $self->line_width() ) {
+         $line  = substr($line, 0, $self->line_width() - length $mark);
          $line .= $mark if $mark;
       }
    }
@@ -2965,7 +3032,7 @@ sub _truncate_line {
 sub _column_error {
    my ( $self, $err ) = @_;
    my $msg = "Column error: $err";
-   $self->{column_errors} eq 'die' ? die $msg : warn $msg;
+   $self->column_errors() eq 'die' ? die $msg : warn $msg;
    return;
 }
 
@@ -4443,7 +4510,7 @@ sub main {
          foreach my $var ( sort keys %$diffs ) {
             $report->add_line($var, @{$diffs->{$var}});
          }
-         $report->set_title(
+         $report->title(
             "$n_diffs config difference" . ($n_diffs > 1 ? 's' : ''));
          print $report->get_report();
       }
diff --git a/bin/pt-online-schema-change b/bin/pt-online-schema-change
index 9ec01041..d65a8ee7 100755
--- a/bin/pt-online-schema-change
+++ b/bin/pt-online-schema-change
@@ -1232,6 +1232,7 @@ sub Mo::import {
             _set_package_isa($caller, @_);
             _set_inherited_metadata($caller);
         },
+        override => \&override,
         has => sub {
             my $names = shift;
             for my $attribute ( ref $names ? @$names : $names ) {
@@ -1528,6 +1529,16 @@ BEGIN {
    }
 }
 
+sub override {
+   my ($methods, $code) = @_;
+   my $caller          = scalar caller;
+
+   for my $method ( ref($methods) ? @$methods : $methods ) {
+      my $full_method     = "${caller}::${method}";
+      *{_glob_for $full_method} = $code;
+   }
+}
+
 }
 1;
 }
@@ -2319,8 +2330,7 @@ sub _d {
 {
 package ReportFormatter;
 
-use strict;
-use warnings FATAL => 'all';
+use Mo;
 use English qw(-no_match_vars);
 use constant PTDEBUG => $ENV{PTDEBUG} || 0;
 
@@ -2330,40 +2340,102 @@ use POSIX qw(ceil);
 eval { require Term::ReadKey };
 my $have_term = $EVAL_ERROR ? 0 : 1;
 
-sub new {
-   my ( $class, %args ) = @_;
-   my @required_args = qw();
-   foreach my $arg ( @required_args ) {
-      die "I need a $arg argument" unless $args{$arg};
-   }
-   my $self = {
-      underline_header     => 1,
-      line_prefix          => '# ',
-      line_width           => 78,
-      column_spacing       => ' ',
-      extend_right         => 0,
-      truncate_line_mark   => '...',
-      column_errors        => 'warn',
-      truncate_header_side => 'left',
-      strip_whitespace     => 1,
-      %args,              # args above can be overriden, args below cannot
-      n_cols              => 0,
-   };
 
-   if ( ($self->{line_width} || '') eq 'auto' ) {
+has underline_header => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has line_prefix => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '# ' },
+);
+has line_width => (
+   is      => 'ro',
+   isa     => 'Int',
+   default => sub { 78 },
+);
+has column_spacing => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { ' ' },
+);
+has extend_right => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { '' },
+);
+has truncate_line_mark => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '...' },
+);
+has column_errors => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'warn' },
+);
+has truncate_header_side => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'left' },
+);
+has strip_whitespace => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has title => (
+   is        => 'rw',
+   isa       => 'Str',
+   predicate => 'has_title',
+);
+
+
+has n_cols => (
+   is      => 'rw',
+   isa     => 'Int',
+   default => sub { 0 },
+   init_arg => undef,
+);
+
+has cols => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_cols',
+);
+
+has lines => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_lines',
+);
+
+has truncate_headers => (
+   is       => 'rw',
+   isa      => 'Bool',
+   default  => sub { undef },
+   init_arg => undef,
+   clearer  => 'clear_truncate_headers',
+);
+
+sub BUILDARGS {
+   my $class = shift;
+   my $args  = $class->SUPER::BUILDARGS(@_);
+
+   if ( ($args->{line_width} || '') eq 'auto' ) {
       die "Cannot auto-detect line width because the Term::ReadKey module "
          . "is not installed" unless $have_term;
-      ($self->{line_width}) = GetTerminalSize();
+      ($args->{line_width}) = GetTerminalSize();
+      PTDEBUG && _d('Line width:', $args->{line_width});
    }
-   PTDEBUG && _d('Line width:', $self->{line_width});
 
-   return bless $self, $class;
-}
-
-sub set_title {
-   my ( $self, $title ) = @_;
-   $self->{title} = $title;
-   return;
+   return $args;
 }
 
 sub set_columns {
@@ -2379,7 +2451,7 @@ sub set_columns {
       die "Column does not have a name" unless defined $col_name;
 
       if ( $col->{width} ) {
-         $col->{width_pct} = ceil(($col->{width} * 100) / $self->{line_width});
+         $col->{width_pct} = ceil(($col->{width} * 100) / $self->line_width());
          PTDEBUG && _d('col:', $col_name, 'width:', $col->{width}, 'chars =',
             $col->{width_pct}, '%');
       }
@@ -2406,10 +2478,10 @@ sub set_columns {
 
       $col->{right_most} = 1 if $i == $#cols;
 
-      push @{$self->{cols}}, $col;
+      push @{$self->cols}, $col;
    }
 
-   $self->{n_cols} = scalar @cols;
+   $self->n_cols( scalar @cols );
 
    if ( ($used_width || 0) > 100 ) {
       die "Total width_pct for all columns is >100%";
@@ -2419,15 +2491,15 @@ sub set_columns {
       my $wid_per_col = int((100 - $used_width) / scalar @auto_width_cols);
       PTDEBUG && _d('Line width left:', (100-$used_width), '%;',
          'each auto width col:', $wid_per_col, '%');
-      map { $self->{cols}->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
+      map { $self->cols->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
    }
 
-   $min_hdr_wid += ($self->{n_cols} - 1) * length $self->{column_spacing};
+   $min_hdr_wid += ($self->n_cols() - 1) * length $self->column_spacing();
    PTDEBUG && _d('min header width:', $min_hdr_wid);
-   if ( $min_hdr_wid > $self->{line_width} ) {
+   if ( $min_hdr_wid > $self->line_width() ) {
       PTDEBUG && _d('Will truncate headers because min header width',
-         $min_hdr_wid, '> line width', $self->{line_width});
-      $self->{truncate_headers} = 1;
+         $min_hdr_wid, '> line width', $self->line_width());
+      $self->truncate_headers(1);
    }
 
    return;
@@ -2436,14 +2508,14 @@ sub set_columns {
 sub add_line {
    my ( $self, @vals ) = @_;
    my $n_vals = scalar @vals;
-   if ( $n_vals != $self->{n_cols} ) {
+   if ( $n_vals != $self->n_cols() ) {
       $self->_column_error("Number of values $n_vals does not match "
-         . "number of columns $self->{n_cols}");
+         . "number of columns " . $self->n_cols());
    }
    for my $i ( 0..($n_vals-1) ) {
-      my $col   = $self->{cols}->[$i];
+      my $col   = $self->cols->[$i];
       my $val   = defined $vals[$i] ? $vals[$i] : $col->{undef_value};
-      if ( $self->{strip_whitespace} ) {
+      if ( $self->strip_whitespace() ) {
          $val =~ s/^\s+//g;
          $val =~ s/\s+$//;
          $vals[$i] = $val;
@@ -2452,7 +2524,7 @@ sub add_line {
       $col->{min_val} = min($width, ($col->{min_val} || $width));
       $col->{max_val} = max($width, ($col->{max_val} || $width));
    }
-   push @{$self->{lines}}, \@vals;
+   push @{$self->lines}, \@vals;
    return;
 }
 
@@ -2460,26 +2532,28 @@ sub get_report {
    my ( $self, %args ) = @_;
 
    $self->_calculate_column_widths();
-   $self->_truncate_headers() if $self->{truncate_headers};
+   if ( $self->truncate_headers() ) {
+      $self->_truncate_headers();
+   }
    $self->_truncate_line_values(%args);
 
    my @col_fmts = $self->_make_column_formats();
-   my $fmt      = ($self->{line_prefix} || '')
-                . join($self->{column_spacing}, @col_fmts);
+   my $fmt      = $self->line_prefix()
+                . join($self->column_spacing(), @col_fmts);
    PTDEBUG && _d('Format:', $fmt);
 
    (my $hdr_fmt = $fmt) =~ s/%([^-])/%-$1/g;
 
    my @lines;
-   push @lines, sprintf "$self->{line_prefix}$self->{title}" if $self->{title};
+   push @lines, $self->line_prefix() . $self->title() if $self->has_title();
    push @lines, $self->_truncate_line(
-         sprintf($hdr_fmt, map { $_->{name} } @{$self->{cols}}),
+         sprintf($hdr_fmt, map { $_->{name} } @{$self->cols}),
          strip => 1,
          mark  => '',
    );
 
-   if ( $self->{underline_header} ) {
-      my @underlines = map { '=' x $_->{print_width} } @{$self->{cols}};
+   if ( $self->underline_header() ) {
+      my @underlines = map { '=' x $_->{print_width} } @{$self->cols};
       push @lines, $self->_truncate_line(
          sprintf($fmt, map { $_ || '' } @underlines),
          mark  => '',
@@ -2490,19 +2564,23 @@ sub get_report {
       my $vals = $_;
       my $i    = 0;
       my @vals = map {
-            my $val = defined $_ ? $_ : $self->{cols}->[$i++]->{undef_value};
+            my $val = defined $_ ? $_ : $self->cols->[$i++]->{undef_value};
             $val = '' if !defined $val;
             $val =~ s/\n/ /g;
             $val;
       } @$vals;
       my $line = sprintf($fmt, @vals);
-      if ( $self->{extend_right} ) {
+      if ( $self->extend_right() ) {
          $line;
       }
       else {
          $self->_truncate_line($line);
       }
-   } @{$self->{lines}};
+   } @{$self->lines};
+
+   $self->clear_cols();
+   $self->clear_lines();
+   $self->clear_truncate_headers();
 
    return join("\n", @lines) . "\n";
 }
@@ -2510,7 +2588,7 @@ sub get_report {
 sub truncate_value {
    my ( $self, $col, $val, $width, $side ) = @_;
    return $val if length $val <= $width;
-   return $val if $col->{right_most} && $self->{extend_right};
+   return $val if $col->{right_most} && $self->extend_right();
    $side  ||= $col->{truncate_side};
    my $mark = $col->{truncate_mark};
    if ( $side eq 'right' ) {
@@ -2530,8 +2608,8 @@ sub _calculate_column_widths {
    my ( $self ) = @_;
 
    my $extra_space = 0;
-   foreach my $col ( @{$self->{cols}} ) {
-      my $print_width = int($self->{line_width} * ($col->{width_pct} / 100));
+   foreach my $col ( @{$self->cols} ) {
+      my $print_width = int($self->line_width() * ($col->{width_pct} / 100));
 
       PTDEBUG && _d('col:', $col->{name}, 'width pct:', $col->{width_pct},
          'char width:', $print_width,
@@ -2555,7 +2633,7 @@ sub _calculate_column_widths {
 
    PTDEBUG && _d('Extra space:', $extra_space);
    while ( $extra_space-- ) {
-      foreach my $col ( @{$self->{cols}} ) {
+      foreach my $col ( @{$self->cols} ) {
          if (    $col->{auto_width}
               && (    $col->{print_width} < $col->{max_val}
                    || $col->{print_width} < $col->{header_width})
@@ -2570,8 +2648,8 @@ sub _calculate_column_widths {
 
 sub _truncate_headers {
    my ( $self, $col ) = @_;
-   my $side = $self->{truncate_header_side};
-   foreach my $col ( @{$self->{cols}} ) {
+   my $side = $self->truncate_header_side();
+   foreach my $col ( @{$self->cols} ) {
       my $col_name    = $col->{name};
       my $print_width = $col->{print_width};
       next if length $col_name <= $print_width;
@@ -2584,10 +2662,10 @@ sub _truncate_headers {
 
 sub _truncate_line_values {
    my ( $self, %args ) = @_;
-   my $n_vals = $self->{n_cols} - 1;
-   foreach my $vals ( @{$self->{lines}} ) {
+   my $n_vals = $self->n_cols() - 1;
+   foreach my $vals ( @{$self->lines} ) {
       for my $i ( 0..$n_vals ) {
-         my $col   = $self->{cols}->[$i];
+         my $col   = $self->cols->[$i];
          my $val   = defined $vals->[$i] ? $vals->[$i] : $col->{undef_value};
          my $width = length $val;
 
@@ -2613,9 +2691,9 @@ sub _truncate_line_values {
 sub _make_column_formats {
    my ( $self ) = @_;
    my @col_fmts;
-   my $n_cols = $self->{n_cols} - 1;
+   my $n_cols = $self->n_cols() - 1;
    for my $i ( 0..$n_cols ) {
-      my $col = $self->{cols}->[$i];
+      my $col = $self->cols->[$i];
 
       my $width = $col->{right_most} && !$col->{right_justify} ? ''
                 : $col->{print_width};
@@ -2628,12 +2706,12 @@ sub _make_column_formats {
 
 sub _truncate_line {
    my ( $self, $line, %args ) = @_;
-   my $mark = defined $args{mark} ? $args{mark} : $self->{truncate_line_mark};
+   my $mark = defined $args{mark} ? $args{mark} : $self->truncate_line_mark();
    if ( $line ) {
       $line =~ s/\s+$// if $args{strip};
       my $len  = length($line);
-      if ( $len > $self->{line_width} ) {
-         $line  = substr($line, 0, $self->{line_width} - length $mark);
+      if ( $len > $self->line_width() ) {
+         $line  = substr($line, 0, $self->line_width() - length $mark);
          $line .= $mark if $mark;
       }
    }
@@ -2643,7 +2721,7 @@ sub _truncate_line {
 sub _column_error {
    my ( $self, $err ) = @_;
    my $msg = "Column error: $err";
-   $self->{column_errors} eq 'die' ? die $msg : warn $msg;
+   $self->column_errors() eq 'die' ? die $msg : warn $msg;
    return;
 }
 
@@ -5686,24 +5764,26 @@ use Time::Local qw(timegm timelocal);
 use Digest::MD5 qw(md5_hex);
 use B qw();
 
-require Exporter;
-our @ISA         = qw(Exporter);
-our %EXPORT_TAGS = ();
-our @EXPORT      = ();
-our @EXPORT_OK   = qw(
-   micro_t
-   percentage_of
-   secs_to_time
-   time_to_secs
-   shorten
-   ts
-   parse_timestamp
-   unix_timestamp
-   any_unix_timestamp
-   make_checksum
-   crc32
-   encode_json
-);
+BEGIN {
+   require Exporter;
+   our @ISA         = qw(Exporter);
+   our %EXPORT_TAGS = ();
+   our @EXPORT      = ();
+   our @EXPORT_OK   = qw(
+      micro_t
+      percentage_of
+      secs_to_time
+      time_to_secs
+      shorten
+      ts
+      parse_timestamp
+      unix_timestamp
+      any_unix_timestamp
+      make_checksum
+      crc32
+      encode_json
+   );
+}
 
 our $mysql_ts  = qr/(\d\d)(\d\d)(\d\d) +(\d+):(\d+):(\d+)(\.\d+)?/;
 our $proper_ts = qr/(\d\d\d\d)-(\d\d)-(\d\d)[T ](\d\d):(\d\d):(\d\d)(\.\d+)?/;
diff --git a/bin/pt-query-advisor b/bin/pt-query-advisor
index 2d622c62..8f88a8d9 100755
--- a/bin/pt-query-advisor
+++ b/bin/pt-query-advisor
@@ -2770,24 +2770,26 @@ use Time::Local qw(timegm timelocal);
 use Digest::MD5 qw(md5_hex);
 use B qw();
 
-require Exporter;
-our @ISA         = qw(Exporter);
-our %EXPORT_TAGS = ();
-our @EXPORT      = ();
-our @EXPORT_OK   = qw(
-   micro_t
-   percentage_of
-   secs_to_time
-   time_to_secs
-   shorten
-   ts
-   parse_timestamp
-   unix_timestamp
-   any_unix_timestamp
-   make_checksum
-   crc32
-   encode_json
-);
+BEGIN {
+   require Exporter;
+   our @ISA         = qw(Exporter);
+   our %EXPORT_TAGS = ();
+   our @EXPORT      = ();
+   our @EXPORT_OK   = qw(
+      micro_t
+      percentage_of
+      secs_to_time
+      time_to_secs
+      shorten
+      ts
+      parse_timestamp
+      unix_timestamp
+      any_unix_timestamp
+      make_checksum
+      crc32
+      encode_json
+   );
+}
 
 our $mysql_ts  = qr/(\d\d)(\d\d)(\d\d) +(\d+):(\d+):(\d+)(\.\d+)?/;
 our $proper_ts = qr/(\d\d\d\d)-(\d\d)-(\d\d)[T ](\d\d):(\d\d):(\d\d)(\.\d+)?/;
@@ -5721,8 +5723,7 @@ sub _d {
 {
 package ReportFormatter;
 
-use strict;
-use warnings FATAL => 'all';
+use Mo;
 use English qw(-no_match_vars);
 use constant PTDEBUG => $ENV{PTDEBUG} || 0;
 
@@ -5732,40 +5733,102 @@ use POSIX qw(ceil);
 eval { require Term::ReadKey };
 my $have_term = $EVAL_ERROR ? 0 : 1;
 
-sub new {
-   my ( $class, %args ) = @_;
-   my @required_args = qw();
-   foreach my $arg ( @required_args ) {
-      die "I need a $arg argument" unless $args{$arg};
-   }
-   my $self = {
-      underline_header     => 1,
-      line_prefix          => '# ',
-      line_width           => 78,
-      column_spacing       => ' ',
-      extend_right         => 0,
-      truncate_line_mark   => '...',
-      column_errors        => 'warn',
-      truncate_header_side => 'left',
-      strip_whitespace     => 1,
-      %args,              # args above can be overriden, args below cannot
-      n_cols              => 0,
-   };
 
-   if ( ($self->{line_width} || '') eq 'auto' ) {
+has underline_header => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has line_prefix => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '# ' },
+);
+has line_width => (
+   is      => 'ro',
+   isa     => 'Int',
+   default => sub { 78 },
+);
+has column_spacing => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { ' ' },
+);
+has extend_right => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { '' },
+);
+has truncate_line_mark => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '...' },
+);
+has column_errors => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'warn' },
+);
+has truncate_header_side => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'left' },
+);
+has strip_whitespace => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has title => (
+   is        => 'rw',
+   isa       => 'Str',
+   predicate => 'has_title',
+);
+
+
+has n_cols => (
+   is      => 'rw',
+   isa     => 'Int',
+   default => sub { 0 },
+   init_arg => undef,
+);
+
+has cols => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_cols',
+);
+
+has lines => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_lines',
+);
+
+has truncate_headers => (
+   is       => 'rw',
+   isa      => 'Bool',
+   default  => sub { undef },
+   init_arg => undef,
+   clearer  => 'clear_truncate_headers',
+);
+
+sub BUILDARGS {
+   my $class = shift;
+   my $args  = $class->SUPER::BUILDARGS(@_);
+
+   if ( ($args->{line_width} || '') eq 'auto' ) {
       die "Cannot auto-detect line width because the Term::ReadKey module "
          . "is not installed" unless $have_term;
-      ($self->{line_width}) = GetTerminalSize();
+      ($args->{line_width}) = GetTerminalSize();
+      PTDEBUG && _d('Line width:', $args->{line_width});
    }
-   PTDEBUG && _d('Line width:', $self->{line_width});
 
-   return bless $self, $class;
-}
-
-sub set_title {
-   my ( $self, $title ) = @_;
-   $self->{title} = $title;
-   return;
+   return $args;
 }
 
 sub set_columns {
@@ -5781,7 +5844,7 @@ sub set_columns {
       die "Column does not have a name" unless defined $col_name;
 
       if ( $col->{width} ) {
-         $col->{width_pct} = ceil(($col->{width} * 100) / $self->{line_width});
+         $col->{width_pct} = ceil(($col->{width} * 100) / $self->line_width());
          PTDEBUG && _d('col:', $col_name, 'width:', $col->{width}, 'chars =',
             $col->{width_pct}, '%');
       }
@@ -5808,10 +5871,10 @@ sub set_columns {
 
       $col->{right_most} = 1 if $i == $#cols;
 
-      push @{$self->{cols}}, $col;
+      push @{$self->cols}, $col;
    }
 
-   $self->{n_cols} = scalar @cols;
+   $self->n_cols( scalar @cols );
 
    if ( ($used_width || 0) > 100 ) {
       die "Total width_pct for all columns is >100%";
@@ -5821,15 +5884,15 @@ sub set_columns {
       my $wid_per_col = int((100 - $used_width) / scalar @auto_width_cols);
       PTDEBUG && _d('Line width left:', (100-$used_width), '%;',
          'each auto width col:', $wid_per_col, '%');
-      map { $self->{cols}->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
+      map { $self->cols->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
    }
 
-   $min_hdr_wid += ($self->{n_cols} - 1) * length $self->{column_spacing};
+   $min_hdr_wid += ($self->n_cols() - 1) * length $self->column_spacing();
    PTDEBUG && _d('min header width:', $min_hdr_wid);
-   if ( $min_hdr_wid > $self->{line_width} ) {
+   if ( $min_hdr_wid > $self->line_width() ) {
       PTDEBUG && _d('Will truncate headers because min header width',
-         $min_hdr_wid, '> line width', $self->{line_width});
-      $self->{truncate_headers} = 1;
+         $min_hdr_wid, '> line width', $self->line_width());
+      $self->truncate_headers(1);
    }
 
    return;
@@ -5838,14 +5901,14 @@ sub set_columns {
 sub add_line {
    my ( $self, @vals ) = @_;
    my $n_vals = scalar @vals;
-   if ( $n_vals != $self->{n_cols} ) {
+   if ( $n_vals != $self->n_cols() ) {
       $self->_column_error("Number of values $n_vals does not match "
-         . "number of columns $self->{n_cols}");
+         . "number of columns " . $self->n_cols());
    }
    for my $i ( 0..($n_vals-1) ) {
-      my $col   = $self->{cols}->[$i];
+      my $col   = $self->cols->[$i];
       my $val   = defined $vals[$i] ? $vals[$i] : $col->{undef_value};
-      if ( $self->{strip_whitespace} ) {
+      if ( $self->strip_whitespace() ) {
          $val =~ s/^\s+//g;
          $val =~ s/\s+$//;
          $vals[$i] = $val;
@@ -5854,7 +5917,7 @@ sub add_line {
       $col->{min_val} = min($width, ($col->{min_val} || $width));
       $col->{max_val} = max($width, ($col->{max_val} || $width));
    }
-   push @{$self->{lines}}, \@vals;
+   push @{$self->lines}, \@vals;
    return;
 }
 
@@ -5862,26 +5925,28 @@ sub get_report {
    my ( $self, %args ) = @_;
 
    $self->_calculate_column_widths();
-   $self->_truncate_headers() if $self->{truncate_headers};
+   if ( $self->truncate_headers() ) {
+      $self->_truncate_headers();
+   }
    $self->_truncate_line_values(%args);
 
    my @col_fmts = $self->_make_column_formats();
-   my $fmt      = ($self->{line_prefix} || '')
-                . join($self->{column_spacing}, @col_fmts);
+   my $fmt      = $self->line_prefix()
+                . join($self->column_spacing(), @col_fmts);
    PTDEBUG && _d('Format:', $fmt);
 
    (my $hdr_fmt = $fmt) =~ s/%([^-])/%-$1/g;
 
    my @lines;
-   push @lines, sprintf "$self->{line_prefix}$self->{title}" if $self->{title};
+   push @lines, $self->line_prefix() . $self->title() if $self->has_title();
    push @lines, $self->_truncate_line(
-         sprintf($hdr_fmt, map { $_->{name} } @{$self->{cols}}),
+         sprintf($hdr_fmt, map { $_->{name} } @{$self->cols}),
          strip => 1,
          mark  => '',
    );
 
-   if ( $self->{underline_header} ) {
-      my @underlines = map { '=' x $_->{print_width} } @{$self->{cols}};
+   if ( $self->underline_header() ) {
+      my @underlines = map { '=' x $_->{print_width} } @{$self->cols};
       push @lines, $self->_truncate_line(
          sprintf($fmt, map { $_ || '' } @underlines),
          mark  => '',
@@ -5892,19 +5957,23 @@ sub get_report {
       my $vals = $_;
       my $i    = 0;
       my @vals = map {
-            my $val = defined $_ ? $_ : $self->{cols}->[$i++]->{undef_value};
+            my $val = defined $_ ? $_ : $self->cols->[$i++]->{undef_value};
             $val = '' if !defined $val;
             $val =~ s/\n/ /g;
             $val;
       } @$vals;
       my $line = sprintf($fmt, @vals);
-      if ( $self->{extend_right} ) {
+      if ( $self->extend_right() ) {
          $line;
       }
       else {
          $self->_truncate_line($line);
       }
-   } @{$self->{lines}};
+   } @{$self->lines};
+
+   $self->clear_cols();
+   $self->clear_lines();
+   $self->clear_truncate_headers();
 
    return join("\n", @lines) . "\n";
 }
@@ -5912,7 +5981,7 @@ sub get_report {
 sub truncate_value {
    my ( $self, $col, $val, $width, $side ) = @_;
    return $val if length $val <= $width;
-   return $val if $col->{right_most} && $self->{extend_right};
+   return $val if $col->{right_most} && $self->extend_right();
    $side  ||= $col->{truncate_side};
    my $mark = $col->{truncate_mark};
    if ( $side eq 'right' ) {
@@ -5932,8 +6001,8 @@ sub _calculate_column_widths {
    my ( $self ) = @_;
 
    my $extra_space = 0;
-   foreach my $col ( @{$self->{cols}} ) {
-      my $print_width = int($self->{line_width} * ($col->{width_pct} / 100));
+   foreach my $col ( @{$self->cols} ) {
+      my $print_width = int($self->line_width() * ($col->{width_pct} / 100));
 
       PTDEBUG && _d('col:', $col->{name}, 'width pct:', $col->{width_pct},
          'char width:', $print_width,
@@ -5957,7 +6026,7 @@ sub _calculate_column_widths {
 
    PTDEBUG && _d('Extra space:', $extra_space);
    while ( $extra_space-- ) {
-      foreach my $col ( @{$self->{cols}} ) {
+      foreach my $col ( @{$self->cols} ) {
          if (    $col->{auto_width}
               && (    $col->{print_width} < $col->{max_val}
                    || $col->{print_width} < $col->{header_width})
@@ -5972,8 +6041,8 @@ sub _calculate_column_widths {
 
 sub _truncate_headers {
    my ( $self, $col ) = @_;
-   my $side = $self->{truncate_header_side};
-   foreach my $col ( @{$self->{cols}} ) {
+   my $side = $self->truncate_header_side();
+   foreach my $col ( @{$self->cols} ) {
       my $col_name    = $col->{name};
       my $print_width = $col->{print_width};
       next if length $col_name <= $print_width;
@@ -5986,10 +6055,10 @@ sub _truncate_headers {
 
 sub _truncate_line_values {
    my ( $self, %args ) = @_;
-   my $n_vals = $self->{n_cols} - 1;
-   foreach my $vals ( @{$self->{lines}} ) {
+   my $n_vals = $self->n_cols() - 1;
+   foreach my $vals ( @{$self->lines} ) {
       for my $i ( 0..$n_vals ) {
-         my $col   = $self->{cols}->[$i];
+         my $col   = $self->cols->[$i];
          my $val   = defined $vals->[$i] ? $vals->[$i] : $col->{undef_value};
          my $width = length $val;
 
@@ -6015,9 +6084,9 @@ sub _truncate_line_values {
 sub _make_column_formats {
    my ( $self ) = @_;
    my @col_fmts;
-   my $n_cols = $self->{n_cols} - 1;
+   my $n_cols = $self->n_cols() - 1;
    for my $i ( 0..$n_cols ) {
-      my $col = $self->{cols}->[$i];
+      my $col = $self->cols->[$i];
 
       my $width = $col->{right_most} && !$col->{right_justify} ? ''
                 : $col->{print_width};
@@ -6030,12 +6099,12 @@ sub _make_column_formats {
 
 sub _truncate_line {
    my ( $self, $line, %args ) = @_;
-   my $mark = defined $args{mark} ? $args{mark} : $self->{truncate_line_mark};
+   my $mark = defined $args{mark} ? $args{mark} : $self->truncate_line_mark();
    if ( $line ) {
       $line =~ s/\s+$// if $args{strip};
       my $len  = length($line);
-      if ( $len > $self->{line_width} ) {
-         $line  = substr($line, 0, $self->{line_width} - length $mark);
+      if ( $len > $self->line_width() ) {
+         $line  = substr($line, 0, $self->line_width() - length $mark);
          $line .= $mark if $mark;
       }
    }
@@ -6045,7 +6114,7 @@ sub _truncate_line {
 sub _column_error {
    my ( $self, $err ) = @_;
    my $msg = "Column error: $err";
-   $self->{column_errors} eq 'die' ? die $msg : warn $msg;
+   $self->column_errors() eq 'die' ? die $msg : warn $msg;
    return;
 }
 
@@ -7850,7 +7919,7 @@ sub main {
             long_last_column => 1,
             extend_right     => 1,
          );
-         $profile->set_title("Profile");
+         $profile->title("Profile");
          $profile->set_columns(
             { name => 'Query ID',                     },
             { name => 'NOTE',     right_justify => 1, },
diff --git a/bin/pt-upgrade b/bin/pt-upgrade
index 63fd6da6..8bea4c6c 100755
--- a/bin/pt-upgrade
+++ b/bin/pt-upgrade
@@ -2025,24 +2025,26 @@ use Time::Local qw(timegm timelocal);
 use Digest::MD5 qw(md5_hex);
 use B qw();
 
-require Exporter;
-our @ISA         = qw(Exporter);
-our %EXPORT_TAGS = ();
-our @EXPORT      = ();
-our @EXPORT_OK   = qw(
-   micro_t
-   percentage_of
-   secs_to_time
-   time_to_secs
-   shorten
-   ts
-   parse_timestamp
-   unix_timestamp
-   any_unix_timestamp
-   make_checksum
-   crc32
-   encode_json
-);
+BEGIN {
+   require Exporter;
+   our @ISA         = qw(Exporter);
+   our %EXPORT_TAGS = ();
+   our @EXPORT      = ();
+   our @EXPORT_OK   = qw(
+      micro_t
+      percentage_of
+      secs_to_time
+      time_to_secs
+      shorten
+      ts
+      parse_timestamp
+      unix_timestamp
+      any_unix_timestamp
+      make_checksum
+      crc32
+      encode_json
+   );
+}
 
 our $mysql_ts  = qr/(\d\d)(\d\d)(\d\d) +(\d+):(\d+):(\d+)(\.\d+)?/;
 our $proper_ts = qr/(\d\d\d\d)-(\d\d)-(\d\d)[T ](\d\d):(\d\d):(\d\d)(\.\d+)?/;
@@ -2984,15 +2986,6 @@ sub calculate_statistical_metrics {
                   $classes->{$class}->{$attrib}->{all},
                   $classes->{$class}->{$attrib}
                );
-
-            if ( $args{apdex_t} && $attrib eq 'Query_time' ) {
-               $class_metrics->{$class}->{$attrib}->{apdex_t} = $args{apdex_t};
-               $class_metrics->{$class}->{$attrib}->{apdex}
-                  = $self->calculate_apdex(
-                     t       => $args{apdex_t},
-                     samples => $classes->{$class}->{$attrib}->{all},
-                  );
-            }
          }
       }
    }
@@ -3117,9 +3110,6 @@ sub metrics {
       median => $metrics->{classes}->{$where}->{$attrib}->{median} || 0,
       pct_95 => $metrics->{classes}->{$where}->{$attrib}->{pct_95} || 0,
       stddev => $metrics->{classes}->{$where}->{$attrib}->{stddev} || 0,
-
-      apdex_t => $metrics->{classes}->{$where}->{$attrib}->{apdex_t},
-      apdex   => $metrics->{classes}->{$where}->{$attrib}->{apdex},
    };
 }
 
@@ -3435,51 +3425,6 @@ sub _deep_copy_attrib_vals {
    return $copy;
 }
 
-sub calculate_apdex {
-   my ( $self, %args ) = @_;
-   my @required_args = qw(t samples);
-   foreach my $arg ( @required_args ) {
-      die "I need a $arg argument" unless $args{$arg};
-   }
-   my ($t, $samples) = @args{@required_args};
-
-   if ( $t <= 0 ) {
-      die "Invalid target threshold (T): $t.  T must be greater than zero";
-   }
-
-   my $f = 4 * $t;
-   PTDEBUG && _d("Apdex T =", $t, "F =", $f);
-
-   my $satisfied  = 0;
-   my $tolerating = 0;
-   my $frustrated = 0;  # just for debug output
-   my $n_samples  = 0;
-   BUCKET:
-   for my $bucket ( keys %$samples ) {
-      my $n_responses   = $samples->{$bucket};
-      my $response_time = $buck_vals[$bucket];
-
-      if ( $response_time <= $t ) {
-         $satisfied += $n_responses;
-      }
-      elsif ( $response_time <= $f ) {
-         $tolerating += $n_responses;
-      }
-      else {
-         $frustrated += $n_responses;
-      }
-
-      $n_samples += $n_responses;
-   }
-
-   my $apdex = sprintf('%.2f', ($satisfied + ($tolerating / 2)) / $n_samples);
-   PTDEBUG && _d($n_samples, "samples,", $satisfied, "satisfied,",
-      $tolerating, "tolerating,", $frustrated, "frustrated, Apdex score:",
-      $apdex);
-
-   return $apdex;
-}
-
 sub _get_value {
    my ( $self, %args ) = @_;
    my ($event, $attrib, $alts) = @args{qw(event attribute alternates)};
@@ -8179,8 +8124,7 @@ sub _d {
 {
 package ReportFormatter;
 
-use strict;
-use warnings FATAL => 'all';
+use Mo;
 use English qw(-no_match_vars);
 use constant PTDEBUG => $ENV{PTDEBUG} || 0;
 
@@ -8190,40 +8134,102 @@ use POSIX qw(ceil);
 eval { require Term::ReadKey };
 my $have_term = $EVAL_ERROR ? 0 : 1;
 
-sub new {
-   my ( $class, %args ) = @_;
-   my @required_args = qw();
-   foreach my $arg ( @required_args ) {
-      die "I need a $arg argument" unless $args{$arg};
-   }
-   my $self = {
-      underline_header     => 1,
-      line_prefix          => '# ',
-      line_width           => 78,
-      column_spacing       => ' ',
-      extend_right         => 0,
-      truncate_line_mark   => '...',
-      column_errors        => 'warn',
-      truncate_header_side => 'left',
-      strip_whitespace     => 1,
-      %args,              # args above can be overriden, args below cannot
-      n_cols              => 0,
-   };
 
-   if ( ($self->{line_width} || '') eq 'auto' ) {
+has underline_header => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has line_prefix => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '# ' },
+);
+has line_width => (
+   is      => 'ro',
+   isa     => 'Int',
+   default => sub { 78 },
+);
+has column_spacing => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { ' ' },
+);
+has extend_right => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { '' },
+);
+has truncate_line_mark => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { '...' },
+);
+has column_errors => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'warn' },
+);
+has truncate_header_side => (
+   is      => 'ro',
+   isa     => 'Str',
+   default => sub { 'left' },
+);
+has strip_whitespace => (
+   is      => 'ro',
+   isa     => 'Bool',
+   default => sub { 1 },
+);
+has title => (
+   is        => 'rw',
+   isa       => 'Str',
+   predicate => 'has_title',
+);
+
+
+has n_cols => (
+   is      => 'rw',
+   isa     => 'Int',
+   default => sub { 0 },
+   init_arg => undef,
+);
+
+has cols => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_cols',
+);
+
+has lines => (
+   is       => 'ro',
+   isa      => 'ArrayRef',
+   init_arg => undef,
+   default  => sub { [] },
+   clearer  => 'clear_lines',
+);
+
+has truncate_headers => (
+   is       => 'rw',
+   isa      => 'Bool',
+   default  => sub { undef },
+   init_arg => undef,
+   clearer  => 'clear_truncate_headers',
+);
+
+sub BUILDARGS {
+   my $class = shift;
+   my $args  = $class->SUPER::BUILDARGS(@_);
+
+   if ( ($args->{line_width} || '') eq 'auto' ) {
       die "Cannot auto-detect line width because the Term::ReadKey module "
          . "is not installed" unless $have_term;
-      ($self->{line_width}) = GetTerminalSize();
+      ($args->{line_width}) = GetTerminalSize();
+      PTDEBUG && _d('Line width:', $args->{line_width});
    }
-   PTDEBUG && _d('Line width:', $self->{line_width});
 
-   return bless $self, $class;
-}
-
-sub set_title {
-   my ( $self, $title ) = @_;
-   $self->{title} = $title;
-   return;
+   return $args;
 }
 
 sub set_columns {
@@ -8239,7 +8245,7 @@ sub set_columns {
       die "Column does not have a name" unless defined $col_name;
 
       if ( $col->{width} ) {
-         $col->{width_pct} = ceil(($col->{width} * 100) / $self->{line_width});
+         $col->{width_pct} = ceil(($col->{width} * 100) / $self->line_width());
          PTDEBUG && _d('col:', $col_name, 'width:', $col->{width}, 'chars =',
             $col->{width_pct}, '%');
       }
@@ -8266,10 +8272,10 @@ sub set_columns {
 
       $col->{right_most} = 1 if $i == $#cols;
 
-      push @{$self->{cols}}, $col;
+      push @{$self->cols}, $col;
    }
 
-   $self->{n_cols} = scalar @cols;
+   $self->n_cols( scalar @cols );
 
    if ( ($used_width || 0) > 100 ) {
       die "Total width_pct for all columns is >100%";
@@ -8279,15 +8285,15 @@ sub set_columns {
       my $wid_per_col = int((100 - $used_width) / scalar @auto_width_cols);
       PTDEBUG && _d('Line width left:', (100-$used_width), '%;',
          'each auto width col:', $wid_per_col, '%');
-      map { $self->{cols}->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
+      map { $self->cols->[$_]->{width_pct} = $wid_per_col } @auto_width_cols;
    }
 
-   $min_hdr_wid += ($self->{n_cols} - 1) * length $self->{column_spacing};
+   $min_hdr_wid += ($self->n_cols() - 1) * length $self->column_spacing();
    PTDEBUG && _d('min header width:', $min_hdr_wid);
-   if ( $min_hdr_wid > $self->{line_width} ) {
+   if ( $min_hdr_wid > $self->line_width() ) {
       PTDEBUG && _d('Will truncate headers because min header width',
-         $min_hdr_wid, '> line width', $self->{line_width});
-      $self->{truncate_headers} = 1;
+         $min_hdr_wid, '> line width', $self->line_width());
+      $self->truncate_headers(1);
    }
 
    return;
@@ -8296,14 +8302,14 @@ sub set_columns {
 sub add_line {
    my ( $self, @vals ) = @_;
    my $n_vals = scalar @vals;
-   if ( $n_vals != $self->{n_cols} ) {
+   if ( $n_vals != $self->n_cols() ) {
       $self->_column_error("Number of values $n_vals does not match "
-         . "number of columns $self->{n_cols}");
+         . "number of columns " . $self->n_cols());
    }
    for my $i ( 0..($n_vals-1) ) {
-      my $col   = $self->{cols}->[$i];
+      my $col   = $self->cols->[$i];
       my $val   = defined $vals[$i] ? $vals[$i] : $col->{undef_value};
-      if ( $self->{strip_whitespace} ) {
+      if ( $self->strip_whitespace() ) {
          $val =~ s/^\s+//g;
          $val =~ s/\s+$//;
          $vals[$i] = $val;
@@ -8312,7 +8318,7 @@ sub add_line {
       $col->{min_val} = min($width, ($col->{min_val} || $width));
       $col->{max_val} = max($width, ($col->{max_val} || $width));
    }
-   push @{$self->{lines}}, \@vals;
+   push @{$self->lines}, \@vals;
    return;
 }
 
@@ -8320,26 +8326,28 @@ sub get_report {
    my ( $self, %args ) = @_;
 
    $self->_calculate_column_widths();
-   $self->_truncate_headers() if $self->{truncate_headers};
+   if ( $self->truncate_headers() ) {
+      $self->_truncate_headers();
+   }
    $self->_truncate_line_values(%args);
 
    my @col_fmts = $self->_make_column_formats();
-   my $fmt      = ($self->{line_prefix} || '')
-                . join($self->{column_spacing}, @col_fmts);
+   my $fmt      = $self->line_prefix()
+                . join($self->column_spacing(), @col_fmts);
    PTDEBUG && _d('Format:', $fmt);
 
    (my $hdr_fmt = $fmt) =~ s/%([^-])/%-$1/g;
 
    my @lines;
-   push @lines, sprintf "$self->{line_prefix}$self->{title}" if $self->{title};
+   push @lines, $self->line_prefix() . $self->title() if $self->has_title();
    push @lines, $self->_truncate_line(
-         sprintf($hdr_fmt, map { $_->{name} } @{$self->{cols}}),
+         sprintf($hdr_fmt, map { $_->{name} } @{$self->cols}),
          strip => 1,
          mark  => '',
    );
 
-   if ( $self->{underline_header} ) {
-      my @underlines = map { '=' x $_->{print_width} } @{$self->{cols}};
+   if ( $self->underline_header() ) {
+      my @underlines = map { '=' x $_->{print_width} } @{$self->cols};
       push @lines, $self->_truncate_line(
          sprintf($fmt, map { $_ || '' } @underlines),
          mark  => '',
@@ -8350,19 +8358,23 @@ sub get_report {
       my $vals = $_;
       my $i    = 0;
       my @vals = map {
-            my $val = defined $_ ? $_ : $self->{cols}->[$i++]->{undef_value};
+            my $val = defined $_ ? $_ : $self->cols->[$i++]->{undef_value};
             $val = '' if !defined $val;
             $val =~ s/\n/ /g;
             $val;
       } @$vals;
       my $line = sprintf($fmt, @vals);
-      if ( $self->{extend_right} ) {
+      if ( $self->extend_right() ) {
          $line;
       }
       else {
          $self->_truncate_line($line);
       }
-   } @{$self->{lines}};
+   } @{$self->lines};
+
+   $self->clear_cols();
+   $self->clear_lines();
+   $self->clear_truncate_headers();
 
    return join("\n", @lines) . "\n";
 }
@@ -8370,7 +8382,7 @@ sub get_report {
 sub truncate_value {
    my ( $self, $col, $val, $width, $side ) = @_;
    return $val if length $val <= $width;
-   return $val if $col->{right_most} && $self->{extend_right};
+   return $val if $col->{right_most} && $self->extend_right();
    $side  ||= $col->{truncate_side};
    my $mark = $col->{truncate_mark};
    if ( $side eq 'right' ) {
@@ -8390,8 +8402,8 @@ sub _calculate_column_widths {
    my ( $self ) = @_;
 
    my $extra_space = 0;
-   foreach my $col ( @{$self->{cols}} ) {
-      my $print_width = int($self->{line_width} * ($col->{width_pct} / 100));
+   foreach my $col ( @{$self->cols} ) {
+      my $print_width = int($self->line_width() * ($col->{width_pct} / 100));
 
       PTDEBUG && _d('col:', $col->{name}, 'width pct:', $col->{width_pct},
          'char width:', $print_width,
@@ -8415,7 +8427,7 @@ sub _calculate_column_widths {
 
    PTDEBUG && _d('Extra space:', $extra_space);
    while ( $extra_space-- ) {
-      foreach my $col ( @{$self->{cols}} ) {
+      foreach my $col ( @{$self->cols} ) {
          if (    $col->{auto_width}
               && (    $col->{print_width} < $col->{max_val}
                    || $col->{print_width} < $col->{header_width})
@@ -8430,8 +8442,8 @@ sub _calculate_column_widths {
 
 sub _truncate_headers {
    my ( $self, $col ) = @_;
-   my $side = $self->{truncate_header_side};
-   foreach my $col ( @{$self->{cols}} ) {
+   my $side = $self->truncate_header_side();
+   foreach my $col ( @{$self->cols} ) {
       my $col_name    = $col->{name};
       my $print_width = $col->{print_width};
       next if length $col_name <= $print_width;
@@ -8444,10 +8456,10 @@ sub _truncate_headers {
 
 sub _truncate_line_values {
    my ( $self, %args ) = @_;
-   my $n_vals = $self->{n_cols} - 1;
-   foreach my $vals ( @{$self->{lines}} ) {
+   my $n_vals = $self->n_cols() - 1;
+   foreach my $vals ( @{$self->lines} ) {
       for my $i ( 0..$n_vals ) {
-         my $col   = $self->{cols}->[$i];
+         my $col   = $self->cols->[$i];
          my $val   = defined $vals->[$i] ? $vals->[$i] : $col->{undef_value};
          my $width = length $val;
 
@@ -8473,9 +8485,9 @@ sub _truncate_line_values {
 sub _make_column_formats {
    my ( $self ) = @_;
    my @col_fmts;
-   my $n_cols = $self->{n_cols} - 1;
+   my $n_cols = $self->n_cols() - 1;
    for my $i ( 0..$n_cols ) {
-      my $col = $self->{cols}->[$i];
+      my $col = $self->cols->[$i];
 
       my $width = $col->{right_most} && !$col->{right_justify} ? ''
                 : $col->{print_width};
@@ -8488,12 +8500,12 @@ sub _make_column_formats {
 
 sub _truncate_line {
    my ( $self, $line, %args ) = @_;
-   my $mark = defined $args{mark} ? $args{mark} : $self->{truncate_line_mark};
+   my $mark = defined $args{mark} ? $args{mark} : $self->truncate_line_mark();
    if ( $line ) {
       $line =~ s/\s+$// if $args{strip};
       my $len  = length($line);
-      if ( $len > $self->{line_width} ) {
-         $line  = substr($line, 0, $self->{line_width} - length $mark);
+      if ( $len > $self->line_width() ) {
+         $line  = substr($line, 0, $self->line_width() - length $mark);
          $line .= $mark if $mark;
       }
    }
@@ -8503,7 +8515,7 @@ sub _truncate_line {
 sub _column_error {
    my ( $self, $err ) = @_;
    my $msg = "Column error: $err";
-   $self->{column_errors} eq 'die' ? die $msg : warn $msg;
+   $self->column_errors() eq 'die' ? die $msg : warn $msg;
    return;
 }
 
@@ -9443,7 +9455,7 @@ sub _report_diff_checksums {
    return unless keys %{$self->{diffs}->{checksums}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Checksum differences');
+   $report->title('Checksum differences');
    $report->set_columns(
       $args{query_id_col},
       @{$args{host_cols}},
@@ -9474,7 +9486,7 @@ sub _report_diff_col_vals {
    return unless keys %{$self->{diffs}->{col_vals}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Column value differences');
+   $report->title('Column value differences');
    $report->set_columns(
       $args{query_id_col},
       {
@@ -9509,7 +9521,7 @@ sub _report_diff_row_counts {
    return unless keys %{$self->{diffs}->{row_counts}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Row count differences');
+   $report->title('Row count differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -9785,7 +9797,7 @@ sub _report_diff_big {
    return unless keys %{$self->{diffs}->{big}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Big query time differences');
+   $report->title('Big query time differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -9822,7 +9834,7 @@ sub _report_diff_in_bucket {
    return unless keys %{$self->{diffs}->{in_bucket}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Significant query time differences');
+   $report->title('Significant query time differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -10141,7 +10153,7 @@ sub _report_diff_warnings {
    return unless keys %{$self->{diffs}->{warnings}};
 
    my $report = new ReportFormatter(extend_right => 1);
-   $report->set_title('New warnings');
+   $report->title('New warnings');
    $report->set_columns(
       $args{query_id_col},
       { name => 'Host', },
@@ -10175,7 +10187,7 @@ sub _report_diff_levels {
    return unless keys %{$self->{diffs}->{levels}};
 
    my $report = new ReportFormatter(extend_right => 1);
-   $report->set_title('Warning level differences');
+   $report->title('Warning level differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -10213,7 +10225,7 @@ sub _report_diff_warning_counts {
    return unless keys %{$self->{diffs}->{warning_counts}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Warning count differences');
+   $report->title('Warning count differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -12375,7 +12387,7 @@ sub report_errors {
    return unless keys %$errors;
 
    my $rf = new ReportFormatter(extend_right=>1);
-   $rf->set_title('Errors');
+   $rf->title('Errors');
    $rf->set_columns(
       { name => 'Query ID' },
       { name => 'Host',    },
diff --git a/lib/CompareQueryTimes.pm b/lib/CompareQueryTimes.pm
index 49053ea3..3faa6cb7 100644
--- a/lib/CompareQueryTimes.pm
+++ b/lib/CompareQueryTimes.pm
@@ -298,7 +298,7 @@ sub _report_diff_big {
    return unless keys %{$self->{diffs}->{big}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Big query time differences');
+   $report->title('Big query time differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -347,7 +347,7 @@ sub _report_diff_in_bucket {
    return unless keys %{$self->{diffs}->{in_bucket}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Significant query time differences');
+   $report->title('Significant query time differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
diff --git a/lib/CompareResults.pm b/lib/CompareResults.pm
index e70effc5..f760a917 100644
--- a/lib/CompareResults.pm
+++ b/lib/CompareResults.pm
@@ -874,7 +874,7 @@ sub _report_diff_checksums {
    return unless keys %{$self->{diffs}->{checksums}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Checksum differences');
+   $report->title('Checksum differences');
    $report->set_columns(
       $args{query_id_col},
       @{$args{host_cols}},
@@ -905,7 +905,7 @@ sub _report_diff_col_vals {
    return unless keys %{$self->{diffs}->{col_vals}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Column value differences');
+   $report->title('Column value differences');
    $report->set_columns(
       $args{query_id_col},
       {
@@ -940,7 +940,7 @@ sub _report_diff_row_counts {
    return unless keys %{$self->{diffs}->{row_counts}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Row count differences');
+   $report->title('Row count differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
diff --git a/lib/CompareWarnings.pm b/lib/CompareWarnings.pm
index 03bf0091..9c79a4c6 100644
--- a/lib/CompareWarnings.pm
+++ b/lib/CompareWarnings.pm
@@ -324,7 +324,7 @@ sub _report_diff_warnings {
    return unless keys %{$self->{diffs}->{warnings}};
 
    my $report = new ReportFormatter(extend_right => 1);
-   $report->set_title('New warnings');
+   $report->title('New warnings');
    $report->set_columns(
       $args{query_id_col},
       { name => 'Host', },
@@ -358,7 +358,7 @@ sub _report_diff_levels {
    return unless keys %{$self->{diffs}->{levels}};
 
    my $report = new ReportFormatter(extend_right => 1);
-   $report->set_title('Warning level differences');
+   $report->title('Warning level differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},
@@ -396,7 +396,7 @@ sub _report_diff_warning_counts {
    return unless keys %{$self->{diffs}->{warning_counts}};
 
    my $report = new ReportFormatter();
-   $report->set_title('Warning count differences');
+   $report->title('Warning count differences');
    my $hostno = 0;
    $report->set_columns(
       $args{query_id_col},