#!/usr/bin/perl
use warnings;
use strict;
no strict "refs";

my %refs;

foreach my $ref (keys %{main::}) {
    if ($ref =~ /::$/) {
        next if ($ref =~ /^main::/);
        recurse($ref);
    } else {
        if (defined \&{$main::{$ref}}) {
            my $sub = \&{$main::{$ref}};
            $refs{$sub} = "main::$ref";
        }
    }
}

sub recurse {
    my ($ref) = @_;
    foreach my $subref (keys %{$ref}) {
        next if ($subref eq $ref);
        if ($subref =~ /::$/) {
            recurse("$ref$subref");
        } else {
            if (defined \&{"$ref$subref"}) {
                $refs{\&{"$ref$subref"}} = "$ref$subref";
            }
        }
    }
}

my $ref = \&Foo::bar;

if ($refs{$ref}) {
    print "ref = $refs{$ref}\n"
} else {
    print "ACK!, can't find $ref\n";
}

package Foo;

sub bar {
    print "Here I am\n";
}