Would this approach be a helpful alternative? (I ask because I'm not sure I entirely understand your real problem space.)

use strict;
use warnings;

#1176332

my $cmd_1 = "perl D:/_scratch/1176332p2.pl";  # (renamed from OP's hel
+lo.pl)
 
open (CMD, "$cmd_1 2>&1|") or warn ("!!! Can't run program: $!\n");
 
while (my $line = <CMD>)  {
     print $line;
         if ($line =~ m/^xyz/)          {
           print "\n Pretending to do some string manipulation\n";
         } else {
           print "(from $0): Nothing yet | ";
         }
     }
close CMD;

[download]
use strict;
use warnings;

# D:/_scratch/1176332p2.pl
 
$| = 1;
 
print "Hello World from 1176332 PART 2\n";
print "Sleeping 10 seconds \n";
 
for (1 .. 10) {
     sleep 1;
     print ". \n";
}
print "xyz \n";

[download]

Execution:

D:\_scratch>D:\_scratch\1176332.pl
Hello World from 1176332 PART 2
(from D:\_scratch\1176332.pl): Nothing yet | Sleeping 10 seconds
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | .
(from D:\_scratch\1176332.pl): Nothing yet | xyz

 Pretending to do some string manipulation

D:\_scratch>

[download]

If I've misconstrued your question or the logic needed to answer it, I offer my apologies to all those electrons which were inconvenienced by the creation of this post.

check Ln42!

In reply to Re: Run and kill external programm after x seconds by ww
in thread Run and kill external programm after x seconds by demichi

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