#!/usr/bin/perl

use strict;
use warnings;

my $testval = "KUNG_FOO=bar";

if ($testval =~ /([\w\_]+)/)
{
	my $keyname = $1;
	print "KEY = [$keyname]\n";
}

exit;

__END__

C:\Steve\Dev\PerlMonks\P-2013-10-16@0800-Underscore>testregex.pl
KEY = [KUNG_FOO]