Keep in mind that you are not trapping ^C or ^Z: you are trapping the signal that the terminal is sending to your process.

If you really want to get the keys, try:

#!/usr/bin/perl -w
use Term::ReadKey;

ReadMode 4;
while (($key=ReadKey(0)) ne 'Q') {
  print "Got key ",ord($key),"\n";
}
ReadMode 0;
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