Term::ReadKey works great, but if you're in a tight loop, there's no need to check it every time; it will slow you down big time. Take a look at this:

use Benchmark;
use Term::ReadKey;

ReadMode cbreak; # make sure we can ctrl-c it

timethese(10, {
    'read_every' =>
        sub { my $cnt = 0; while ($cnt < 1e5) { print "$cnt\n" if Read
+Key(-1); $cnt++ } },
    'read_1000'  =>
        sub { my $cnt = 0; while ($cnt < 1e5) { print "$cnt\n" if not 
+$cnt % 1000 and ReadKey(-1); $cnt++ } }
});

ReadMode restore; # Reset tty mode before exiting

[brad:foo]$ perl read_test.pl
Benchmark: timing 10 iterations of read_1000, read_every...
 read_1000:  2 wallclock secs ( 1.18 usr +  0.04 sys =  1.22 CPU) @  8
+.20/s (n=10)
read_every: 42 wallclock secs (29.19 usr + 10.88 sys = 40.07 CPU) @  0
+.25/s (n=10)
[download]

Reading only every 1000 iterations, at least in this test, still catches every keystroke immediately.

Brad