Hi Discipulus. Just few line changes ( 3 places ). Here's the diff output.

$ diff pm-cb-g pm-cb-g-hobo
27,28c27,28
< use threads (stack_size => 2 ** $stack_size);
< use Thread::Queue;
---
> use MCE::Hobo;
> use MCE::Shared;
41c41
< my ($readQ, $writeQ) = map 'Thread::Queue'->new, 1, 2;
---
> my ($readQ, $writeQ) = map { MCE::Shared->queue() } 1, 2;
43c43
< my $communicate_t = threads->create(\&communicate);
---
> my $communicate_t = MCE::Hobo->create(\&communicate);
[download]

Update. The stack_size option isn't needed when using MCE::Hobo. Below is the diff -u output.

$ diff -u pm-cb-g pm-cb-g-hobo
--- pm-cb-g    2017-07-07 16:05:39.000000000 -0500
+++ pm-cb-g-hobo    2017-07-07 16:32:36.782646208 -0500
@@ -6,12 +6,11 @@

 use Getopt::Long qw( :config no_ignore_case );

-my ($bg_color, $fg_color, $author_color, $font_name, $char_size,
-    $stack_size);
+my ($bg_color, $fg_color, $author_color, $font_name, $char_size);

 BEGIN {
     ($bg_color, $fg_color, $author_color, $font_name, $char_size,
-     $stack_size) = qw( white black blue Helvetica 12 15 );
+    ) = qw( white black blue Helvetica 12 );

     die "Invalid arguments!\n" unless GetOptions(
         'a|author_color=s' => \$author_color,
@@ -19,13 +18,12 @@
         'c|char_size=i'    => \$char_size,
         'f|fg_color=s'     => \$fg_color,
         'F|font_name=s'    => \$font_name,
-        's|stack_size=i'   => \$stack_size,
     );
 }


-use threads (stack_size => 2 ** $stack_size);
-use Thread::Queue;
+use MCE::Hobo;
+use MCE::Shared;


 use constant {
@@ -38,9 +36,9 @@
 };


-my ($readQ, $writeQ) = map 'Thread::Queue'->new, 1, 2;
+my ($readQ, $writeQ) = map { MCE::Shared->queue() } 1, 2;

-my $communicate_t = threads->create(\&communicate);
+my $communicate_t = MCE::Hobo->create(\&communicate);

 gui();
[download]

Regards, Mario