The signal handler is that sub{} that you stored in $SIG{ALRM}.

To kill the other script, you'd have to get its pid. Unfortunately I don't know any way to this without any ugly hacks. Maybe someone else does.

So for instance, you can use this temporary file handle hack:

#!/usr/bin/perl
use strict;
use warnings;
use CGI;
use File::Temp;
 
my $q = new CGI;
 
print $q->header;

my $tmp = File::Temp->new(UNLINK => 0);
my $tmpnam = $tmp->filename;
 
eval {
   local %SIG;
   $SIG{ALRM}=
     sub{
         $tmp->close;
         system("fuser", "-sk", "-TERM", $tmpnam);
         unlink $tmpnam;
         die "timeout reached, after 20 seconds!\n";
     };
   alarm 3;
   
   #sleep (60);
   system("sleep 10 3>$tmpnam");
 
   alarm 0;
};
 
alarm 0;
 
if($@) { print "Error: $@\n"; }
 
exit(0);
[download]

This requires the "fuser" command, which is shipped with most Linux distros.

If this does not make the other script die, then leave out the "-TERM".

I replaced the name of your shell script with "sleep 10", otherwise I can't test it. I also replaced 20 with 3 because I did not want to wait 20 seconds.

Thank You @betterworld for the line: system("sleep 10 3>$tmpnam"); what does 3>$tmpnam do? If I need to replace the sleep 10 with a call to script that needs arguments, how would I do that? i.e: system("/opt/bea/domains/fsa/scripts/start.sh fsaAs02 -q 3>$tmpnam");