#!/usr/bin/perl

use warnings;
use strict;

my $test = "TEST TESt TE'st T 12TE";
while ($test =~ /(?<![\pL\pN\'-])       #NOT a hyphen, apostroph, letter or number before
                 (\p{Lu}{2,})           # two or more uppercase letters
                 (?![\pL\pN\'-])        #NOT a hyphen, apostroph, letter or number after
                /xg) 
{  
    print "$1\n";
}