This task can be solved with several nested greps. But if you want proper amb just for the joy of it — the following code is somewhat close. 

use warnings;
use strict;
use Carp;

sub need 
{
        my $cond = shift;
        croak 'require failed' if (!$cond);
}

sub which_1
{
        my ($code, $vals) = @_;
        for my $param (@{$vals}) {
                if (my $res = eval { &{$code}($param); return 1; }) {
                        return $param;
                }
        }
        croak 'no match';
}

my @floors = (1..5);
print which_1 sub { my $p = shift; need($p == 3); }, \@floors;

[download]

The which_1 sub returns whichever element of an array (passed as a reference in a second arg) first matches all the needs in the code reference (first arg).

One can generalize this to an arbitrary number of array references using currying. I may do this later, when I have more time.

Remember — continuations can (and should) usually be replaced with closures or threads.

In reply to Re: How implement AMB in perl? by akho
in thread How implement AMB in perl? by xiaoyafeng

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