#!/usr/bin/perl -w
use strict;
use warnings;

my %foo = (
    test    => {
        alpha   => 'beta',
        gamma   => 'delta',
    },
);
foreach my $nr (keys %{$foo{test}}) {
    $foo{zaehler} = $nr;
    test (\%foo);
}
sub test {
    my ($bar) = @_;
    print "habe " . $bar -> {zaehler} . "\n";
}