As noted, you will need to use the system(...) or `...` to execute any system-level commands. These commands will wait for the external processes to complete.

But you mentioned you would like to try using fork and wait/waitpid, so try this example:

    my $pid;
    if (defined($pid = fork)) {
        if ($pid) {
            &parent();
        } else {
            &child();
        }
    } else {
        die "Fork didn't work...\n";
    }

    sub child {
        print "Running child process instructions...\n";
        sleep 5;
    # If you have system-level commands to process,
    # you will still need to use system(...) or `...`
        exit;
    }

    sub parent {
        waitpid($pid,0); # Will wait for a specific child process
    #   wait;            # Will wait for ANY child process to finish
        print "Finished waiting for child process $pid\n";
    }
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