Here is the code I have been developing. I am trying to make the debug mode (as set by $foo->debug(1)) able to give a better hint as to what is happening at expense of execution speed.

use strict;
package Persistent::Code;

sub new
{
    my ($class,$src,$permflag) = @_;
    my %flags;
    $flags{'perm'} = 1 if $permflag;

    my $cr = eval "sub { $src }";
    return undef if $@;
    my $self = [$cr,$src,\%flags];
    bless $self, $class;
}

sub src
{
    my $self = shift;
    
    $self->[1];
}

sub coderef
{
    my $self = shift;
    
    $self->[0];
}

sub debug
{
    my $self = shift;
    
    @_ ? ($self->[2]{debug} = shift) : $self->[2]{debug};
}

sub perm
{
    my $self = shift;
    
    @_ ? ($self->[2]{perm} = shift) : $self->[2]{perm};
}

sub run
{
    my $self = shift;
    my $pkg = ref $self;
    
    if ($self->[2]{debug})
    {
        my $src = $self->[1];
        print "eval: ",$src;
        
        wantarray ? eval "(&sub {$src}(@_))"  : eval "&sub {$src}(@_)"
+;
    } else
    {
        goto &{$self->[0]};
    }
}

sub STORABLE_freeze
{
    my ($self,$cloning) = @_;
    
    $self->[2]{perm} ? $self->[1] : '';
}

sub STORABLE_thaw
{
    my ($obj,$cloning,$code) = @_;
    
    return if !$code;
    my $class = ref $obj;
    my $newobj = $class->new($code,'perm');
    
    @$obj = @$newobj;
}

1;
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