package Devel::REPL::Plugin::OutputCache; use Devel::REPL::Plugin; use namespace::clean -except => [ 'meta' ]; has output_cache => ( is => 'rw', isa => 'ArrayRef', default => sub { [] }, lazy => 1, ); has warned_about_underscore => ( is => 'rw', isa => 'Bool', default => 0, lazy => 1, ); around 'eval' => sub { my $orig = shift; my ($self, $line) = @_; my $has_underscore = *_{CODE}; if ($has_underscore && !$self->warned_about_underscore) { warn "OutputCache: Sub _ already defined."; $self->warned_about_underscore(1); } else { # if _ is removed, then we should warn about it again if it comes back $self->warned_about_underscore(0); } # this needs to be a postfix conditional for 'local' to work local *_ = sub () { $self->output_cache->[-1] } unless $has_underscore; my @ret; if (wantarray) { @ret = $self->$orig($line); } else { $ret[0] = $self->$orig($line); } push @{ $self->output_cache }, @ret > 1 ? \@ret : $ret[0]; return wantarray ? @ret : $ret[0]; }; 1; __END__ =head1 NAME Devel::REPL::Plugin::OutputCache - remember past results, _ is most recent =head1 SYNOPSIS > 21 / 7 3 > _ * _ 9 > sub { die "later" } sub { die "later" } > _->() Runtime error: later =head1 DESCRIPTION Re-using results is very useful when working in a REPL. With C you get C<_>, which holds the past result. The benefit is that you can build up your result instead of having to type it in all at once, or store it in intermediate variables. C also provides C<< $_REPL->output_cache >>, an array reference of all results in this session. Devel::REPL already has a similar plugin, L. There are some key differences though: =over 4 =item Input vs Output C remembers input. C remembers output. =item Munging vs Pure Perl C performs regular expressions on your input. C provides the C<_> sub as a hook to get the most recent result, and C<< $_REPL->output_cache >> for any other results. =item Principle of Least Surprise C will replace exclamation points in any part of the input. This is problematic if you accidentally include one in a string, or in a C expression. C uses a regular (if oddly named) subroutine so Perl does the parsing -- no surprises. =back =head1 CAVEATS The C<_> sub is shared across all packages. This means that if a module is using the C<_> sub, then there is a conflict and you should not use this plugin. For example, L uses the C<_> sub for localization. Jifty is the only known user. =head1 SEE ALSO C, C =head1 AUTHOR Shawn M Moore, C<< >> =head1 COPYRIGHT AND LICENSE Copyright (C) 2007 by Shawn M Moore This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =cut