#!/usr/bin/env perl 

use strict;
use warnings;

use List::Util qw{ first };

my %hash = (
    ASD => 1,
    ZXC => 2,
    QWE => 3,
    TYU => 4
);

my $val = "qwe";
if(my $res = first { lc $_ eq $val } keys %hash) {
    print "Found: $res\n";
} else {
    print "Not found\n";
};