use strict;
use warnings;

my %hash1 = (TEXT => 25, Text => 25, Wibble => 20);
my %hash2 = (text => 25, TexT => 25, wibble => 20);
my %h1Keys;
my %h2Keys;

push @{$h1Keys{lc $_}}, $_ for keys %hash1;
push @{$h2Keys{lc $_}}, $_ for keys %hash2;

my @common = grep {exists $h2Keys{$_}} keys %h1Keys;

print "Hash 1 keys \[@{$h1Keys{$_}}\] match \[@{$h2Keys{$_}}\] in hash 2\n"
    for @common;