Hi Garden Dwarf,

Based on your code, the following runs for me on a Windows 7 VM running Perl 5.26.1. Workers persist in the background. Two queues (inbound and outbound) are used. Due to lack of time, I apologize for not displaying to the terminal. The goal was seeing text display in the windows dialog. And yes, there you go. :)

I added a state variable ($running) in the event a long running job so not to impact the main app.

#!/bin/perl

# Win32::GUI and threads issue
# https://www.perlmonks.org/?node_id=1228580

use strict;
use warnings;

# One may run threads + MCE::Shared. This works very well.
# Why MCE::Shared one might ask? Well, it handles serialization
# of data objects automatically. E.g. passing array refs.

use threads;
use MCE::Shared;

my $queue_in = MCE::Shared->queue();
my $queue_ou = MCE::Shared->queue();

my $t_amount = 3; # Amount of threads to create
my $running  = 0;
my $textbox;
my $win;

# Important, spawn threads early before loading Win32::GUI.
threads->new('producer') for 1..$t_amount;

# Run the main app or consumer afterwards.
consumer();

# Voila :)
exit;

sub consumer {
  require Win32::GUI;

  # Initialize window
  $win = new Win32::GUI::Window(
      -left   => 0,
      -top    => 0,
      -width  => 300,
      -height => 300,
      -name   => "Window",
      -text   => "Test",
  );

  $win->InvalidateRect(1);

  $textbox = $win->AddTextfield(
    -name      => "Output",
    -left      => 5,
    -top       => 5,
    -width     => 275,
    -height    => 255,
    -text      => "",
    -multiline => 1,
  );

  # Start application (calls draw_Timer)
  $win->AddTimer('draw', 333);
  $win->Show();

  Win32::GUI::Dialog();
}

sub producer {
  $SIG{QUIT} = sub {
    threads->exit();
  };
  while ( defined ( my $next_args = $queue_in->dequeue ) ) {
    my ( $c, $begin, $end ) = @{ $next_args };
    my @ret = compute($begin, $end);
    sleep 2; # simulate a long running process
    $queue_ou->enqueue([ $c, @ret ]);
  }
}

sub Window_Terminate {
  $queue_in->end();
  $_->kill('QUIT') for threads->list;
  -1;
}

sub draw_Timer {
  # Enqueue range of computation to background threads
  if ( $running == 0 ) {
    $running = 1;
    foreach my $c (1..$t_amount) {
      my $d = $c - 1;
      $queue_in->enqueue([ $c, $d*10, $d*10+10 ]);
    }
  }
  # Obtain data once background threads have completed
  if ( $running == 1 && $queue_ou->pending == $t_amount ) {
    $running = 0;
    my @ordered_ret;
    foreach my $c (1..$t_amount) {
      my $ret  = $queue_ou->dequeue();
      my $c    = shift(@{ $ret }) - 1; # array-based-zero
      $ordered_ret[$c] = "";
      foreach my $data (@{ $ret }) {
        $ordered_ret[$c] .= "|".$data;
      }
      $ordered_ret[$c] .= "\n";
    }
    $textbox->Append($_) for @ordered_ret;
  }
}

sub compute {
  my ($begin, $end) = (shift, shift);
  my (@tbl, $cpt);
  for ($cpt = $begin; $cpt < $end; $cpt++) {
    push @tbl, $cpt;
  }
  return @tbl;
}
[download]

Regards, Mario

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