Actually I found another problem that was causing me confusion. I was closing the filehandle after opening it. (at your suggestion :-)) This was what was causing my script to not execute until after the app was closed, making me believe that it was not running in the background. I don't know why closing the filehandle would affect it this way though.

Try this: (after 10 sec the script will run)

#!/usr/bin/perl

use strict;

my $pid = open my $fh, 'sleep 10  |'
    or die "Couldn't spawn: $! / $?";
    
close $fh;

print "Spawned child as $pid";
print "Doing own work $_\n" for 1..10;

print "Killing child $pid\n";
kill 9 => $pid;
print "done\n";
[download]

ps: is it appropriate to call a process that runs in the background a "child"? It seems like it is disassociated from the "parent".