=over =item select FILEHANDLE X This calls the select(2) syscall with the bit masks specified, which can be constructed using C and C, along these lines: $rin = $win = $ein = ''; vec($rin,fileno(STDIN),1) = 1; vec($win,fileno(STDOUT),1) = 1; $ein = $rin | $win; If you want to select on many filehandles, you may wish to write a subroutine like this: sub fhbits { my(@fhlist) = split(' ',$_[0]); my($bits); for (@fhlist) { vec($bits,fileno($_),1) = 1; } $bits; } $rin = fhbits('STDIN TTY SOCK'); The usual idiom is: ($nfound,$timeleft) = select($rout=$rin, $wout=$win, $eout=$ein, $timeout); or to block until something becomes ready just do this $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef); Most systems do not bother to return anything useful in $timeleft, so calling select() in scalar context just returns $nfound. Any of the bit masks can also be undef. The timeout, if specified, is in seconds, which may be fractional. Note: not all implementations are capable of returning the $timeleft. If not, they always return $timeleft equal to the supplied $timeout. You can effect a sleep of 250 milliseconds this way: select(undef, undef, undef, 0.25); Note that whether C. On error, C, except as permitted by POSIX, and even then only on POSIX systems. You have to use C instead. =back