package Lambda;

use strict;
use warnings;

use Exporter qw( import );

our @EXPORT = qw( lambda );

sub _on_destroy(&@) {
    return bless([@_], 'Lambda::OnDestroy');
}

sub Lambda::OnDestroy::DESTROY {
    my ($self) = @_;
    my ($cb, @args) = @$self;
    $cb->(@args) if $cb;
}

sub lambda {
    my $xr = \$_[0];
    my $f  =  $_[1];
    return sub {
        my $temp = $$xr;
        $$xr = $_[0];
        my $sentry = _on_destroy { $$xr = $temp; };
        return $f->();
    }
}

1;