Update: Added missing line after looping each region.

Update: This example runs nearly as fast as serial code and completes in 14.5 seconds without threads.

The following demo demonstrates multiple workers with a single writer running simultaneously. Locking between workers is handled automatically by MCE.

use strict;
use warnings;

use Excel::Writer::XLSX;
use MCE::Loop Sereal => 1;

my $nodeList = [
   [ 'AMS' , 'a'  ],
   [ 'APJ' , 'ap' ],
   [ 'EMEA', 'e'  ],
];

my ($workbook, %worksheets, $format);

$workbook = Excel::Writer::XLSX->new("Node_List.xlsx");
$workbook->set_properties(
   title    => 'Node List',
   author   => 'L_WC demo',
   comments => 'Node List',
);

$format = $workbook->add_format(bg_color => 44);
$format->set_align('center');

foreach (@{ $nodeList }) {
   $worksheets{ $_->[0] } = $workbook->add_worksheet( $_->[0] );
}

MCE::Loop::init(
   chunk_size => 1, max_workers => scalar(@{ $nodeList }),
   gather => sub {
      my $region = shift;
      while (@{ $_[0] }) {
         my @args = splice(@{ $_[0] }, 0, 3);
         $worksheets{$region}->write(@args, $format)
      }
   },
);

mce_loop { doSomething($_->[0], $_->[1]) } $nodeList;

$workbook->close();

print "Node List is Done.\n";

sub doSomething {
   my ($region, $sql) = @_;

   if ($region eq 'AMS') {
      my @data; my $n = $region . '_';
      for (0..65534) {
         push @data, $_, 0, $n . $_;
         push @data, $_, 1, $_ + 4;
         push @data, $_, 2, $_ + 3;
         push @data, $_, 3, $_ + 2;
         push @data, $_, 4, $_ + 1;
         if ($_ % 4000 == 0) {
            MCE->gather($region, \@data);
            @data = ();
         }
      }
      MCE->gather($region, \@data) if @data;
      print "AMS  -----DONE.\n";
   }
   elsif ($region eq 'APJ') {
      my @data; my $n = $region . '_';
      for (0..65534) {
         push @data, $_, 0, $n . $_;
         push @data, $_, 1, $_ + 1;
         push @data, $_, 2, $_ + 3;
         push @data, $_, 3, $_ + 4;
         push @data, $_, 4, $_ + 2;
         if ($_ % 4000 == 0) {
            MCE->gather($region, \@data);
            @data = ();
         }
      }
      MCE->gather($region, \@data) if @data;
      print "APJ  -----DONE.\n";
   }
   elsif ($region eq 'EMEA') {
      my @data; my $n = $region . '_';
      for (0..65534) {
         push @data, $_, 0, $n . $_;
         push @data, $_, 1, $_ + 1;
         push @data, $_, 2, $_ + 2;
         push @data, $_, 3, $_ + 3;
         push @data, $_, 4, $_ + 4;
         if ($_ % 4000 == 0) {
            MCE->gather($region, \@data);
            @data = ();
         }
      }
      MCE->gather($region, \@data) if @data;
      print "EMEA -----DONE.\n";
   }

   return;
}
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Kind regards, Mario