wrapper script to run a command with a timeout

timeout.pl

use POSIX qw(WNOHANG WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG);
use Time::HiRes qw(gettimeofday);

die "usage: $0 TIMEOUT COMMAND ...\n" if (@ARGV < 2);

$timeout = shift @ARGV;
$pid = fork();
die "fork: $!" if not defined $pid;
if ($pid == 0) {
 exec @ARGV or die "$ARGV[0]: $!";
}

$SIG{"CHLD"} = sub { 
 waitpid $pid, WNOHANG;
 exit WEXITSTATUS($?) if WIFEXITED($?);
 if (WIFSIGNALED($?)) {
  kill WTERMSIG($?), $$;
  # Still here?  Signal was handled, so just report it and exit.
  die "Signal ${WTERMSIG($?)}";
 } 
};

$endtime = gettimeofday()+$timeout;
sleep($endtime-gettimeofday()) while (gettimeofday() < $endtime);
print STDERR "timeout!\n";
kill "TERM", $pid;
while (1) { sleep(1) }

Could use a second timeout with a hard kill.
Doesn't try to relay signals. It could run in the background, and poll. Polling is ugly, and it could mistarget the wrong process when pids are recycled.