%cat = (
    'C[AEIOU]NWAY' => 'AAA',
    '(BOSTON|CHICAGO)' => 'BBB',
    '(LAS VEGAS|NEVADA)' => 'CCC',
    '(DALLAS|AUSTIN)' => 'DDD',  
    '(NASHVILLE|M[AEIOU]MPHIS)' => 'EEE'    
);

$variable = 'CHICAGO';
for (keys %cat) {
  next unless $variable =~ /$_/;
  print "$variable maps to $cat{$_}\n";
  last;
}