use strict;
use warnings;
use feature 'say';
use Scope::Upper qw/ unwind :words /;

sub my_grep (&@) {
    my $code = shift;
    my @out;
    for ( @_ ) {

        say "in @{[ (caller(0))[3] ]}, processing the $_";

        my $result = &{ $code };
        unwind @out, UP UP if $result eq 'leave';
        push @out, $result
    }
    return @out;
}

sub maybe_working {
    my @out = my_grep { return /4/ ? 'leave' : $_ } 1 .. 5;
    
    say 'still here, but you won\'t see this line!';
    
    return @out;
}

say "in final output: $_" for maybe_working;
say 'exiting...';