#!/usr/bin/perl
use strict;

sub sys_alarm {
  my ( $cmd_result, $pid );
  my $cmd = shift( @_ );
  my $timeout = shift( @_ );
  eval {
    local $SIG{ ALRM } = sub {
      kill -9, $pid;
      warn "timeout of command \"$cmd\"; killing $pid\n";
    };
    if ($pid = open(IN, "-|")) {
      alarm $timeout;
      while ( <IN>) {
        $cmd_result .= $_;
      }
      close(IN);
      waitpid $pid, 0;
      alarm 0;
    } else {
      die "cannot fork: $!" unless defined $pid;
      setpgrp( 0, 0 );
      exec( $cmd );
      exit;
    }
  };
  return $cmd_result;
}
my $x =  sys_alarm("sleep 10; echo foo", 5);
print "Output: " . $x  . "\n\n";