For $work I'm writing a text-only menu system, and that defines callbacks which are called for specific input.

Now the default behavior is to simply ignore the return value (trust me, it makes sense in my $work context), and exit the menu when the input is empty. However I want to give some callbacks the possibility to exit the menu too.

How? A normal return() doesn't accomplish that, so here is my hack: 

use strict;
use warnings;
use 5.010;

my @return_stack;

sub RETURN {
    push @return_stack, [@_];
    no warnings 'exiting';
    last 'UNIQUELABEL';
}


sub menu {
UNIQUELABEL:
    while (1) {
        for (@_) {
            $_->();
        }
    }

    return @{pop @return_stack};
};

say menu
    sub { say 'go on'    },
    sub {
        RETURN menu 
            sub { say 'still here' },
            sub { RETURN 'ended'   },
            sub { 'never called'   },
    },
    sub { 'never called'   },
   ;
__END__
go on
still here
ended

[download]

In my menu system, the inner loop is a bit different, but this captures the idea pretty well IMHO.

The same could be achieved through exceptions.

One thing it doesn't handle well is context: the callback is always called in the same context (here void context), so wantarray isn't useful in the callback.

Perl 6 - the future is here, just unevenly distributed

In reply to Non-local return via last() by moritz

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