#!/usr/bin/perl

require 5.6.1;
use strict;

my $hash;

$hash = {
  a => {
    b=> [ 
      \\\$hash,
      {
        c => sub { 
          $_ = shift;
          return [ join "","j",$_,"h" ];
        }
      }
    ]
  }
};



sub retrievekey {
  my $endvalue = shift;
  my $keys = shift;
  my @keys = split /\./, $keys;
  foreach my $x (@keys) {
    return undef unless defined $endvalue;
    $endvalue = $$endvalue while (ref($endvalue) eq "REF");
    eval {
      if (ref($endvalue) eq "HASH") {
        $endvalue = $endvalue->{$x};
      } elsif (ref($endvalue) eq "ARRAY") {
        $endvalue = $endvalue->[$x];
      } elsif (ref($endvalue) eq "CODE") {
        $endvalue = $endvalue->($x);
      } else { return undef; }
    };
    return undef if ($@);
  }
  $endvalue;
}

print retrievekey($hash, 'a.b.0.a.b.1.c.ap.0'),$/;
__DATA__
output:
japh