Probably the easiest, and most portable (since, apparently, Windows perl only supports select for sockets, not to mention that it probably doesn't support termios.), way to do this would be to use Term::ReadKey:

use Term::ReadKey;

for (;;) {
  if (defined(my $c = ReadKey(-1))) {
    # got a character $c, process
  }
  # do other stuff
}
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