$pid = fork;

##</code><code>##

      eval {
        alarm $timeout;
        $result = `$solver $file`;
        waitpid($pid, 0);
      };

##</code><code>##

my $pid = fork();
die "failed to fork" unless defined $pid;
if ($pid) {
  # we are parent. do things
} else {
  # we are child. do other things
}