First off please use code tags so your code is readable - I have done this for you this time around. 

my $pid = fork; 
if ($pid > 0){ 

     eval{ 
         local $SIG{ALRM} = sub {kill 9, -$PID; die "TIMEOUT!"}; 
         alarm $num_secs_to_timeout; 
         waitpid($pid, 0); 
         alarm 0; 
     }; 

} elsif($pid == 0){ 
       setpgrp(0,0); 
       exec('echo blahblah | program_of_interest'); 
       exit(0); 
}

[download]

Documentation for fork will show you that the fork call returns the pid of the forked process to the parent and 0 to the child. This is used above to run the parent through the if and the child through the else above.

The following should help you understand the rest:

  1. setpgrp
  2. exec
  3. Piped redirection of input and output
  4. How to use Alarm to timeout

This code essentially creates a process which executes a non-perl program on a timeout.

In reply to Re: code explanation by tmharish
in thread code explanation by venky4289

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