my $key_buf;
my $sequence = qr/some_keys/g;

system "stty cbreak < /dev/tty > /dev/tty 2>&1";
while (($key=getc) ) {
                                                            
    $key_buf .= $key;
    if ($key_buf =~ $my_sequence) {
        system "xmessage 'OH YA!'";
        last;
    }
    last if $key eq "q";
}

system "stty -cbreak < /dev/tty > /dev/tty 2>&1";