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

my %hash1 = (TEXT => 25, Text => 25, Wibble => 20, foo=>42, BAZ => 0);
my %hash2 = (text => 25, TexT => 25, wibble => 20, bar=>43, bAz => -1);

my @dups = do{
	local %_;
	$_{$_}++ for(map lc, (keys %hash1, keys %hash2));
	delete @_{map $_{$_} == 1 ? $_ : (), keys %_};
	sort keys %_;
};

print "@dups \n";