#!/usr/bin/perl -w 
use Data::Dumper; 
my $hashtest; 
$hashtest->{'abc'}->{'filename'} = 'fred'; $hashtest->{'def'}->{'filename'} = 'harry'; 
 
foreach $v (values (%{$hashtest})) 
{ 
    $testhash->{$v->{'filename'}} = 1; 
} 
print Dumper($testhash);