gistfile1.pl

#!/usr/bin/perl 
use strict;
use warnings;

# A proof of concept for a next generation context object
# that doesn't require the use of local and direct access
# to the stash HASH reference.
#
# pros:
# no use of local
# no manual (error prone) stack management
#
# cons:
# cloning of entire stash structure each time is probably expensive
#

package Mock::Context;

use base 'Exporter';
use vars qw(@EXPORT @EXPORT_OK);
@EXPORT = @EXPORT_OK = qw(context_scope);

use Storable qw(dclone);

sub new { bless { stack => [] }, __PACKAGE__; }

sub stash {
    my $ctx   = shift;
    my $stack = $ctx->{stack};
    push @$stack, $_[0] if defined $_[0];
    return @$stack[-1];
}

sub context_scope (&;@) {
    my ( $code, $ctx ) = @_;
    local $ctx->{stack} = dclone( $ctx->{stack} );
    $code->();
}

package main;

my $ctx = Mock::Context->new;

$ctx->stash(40);
print $ctx->stash . "\n"; # value set

eval {    # prove error would not foil the stash going back to its value
    Mock::Context::context_scope { # temporary scope of context changes 
        $ctx->stash(72);
        print $ctx->stash . "\n"; # locally scope value is set 
        die "!!!!";
    }
    $ctx;
};

print $@ if $@; # prove the "error" happened

print $ctx->stash . "\n"; # prove the stash was returned to its original value