Hi tybalt89,

Using your solution, I tried adding exception support in the event the worker died.

#!/usr/bin/perl

use strict;
use warnings;
use feature 'say';

use Storable qw( freeze thaw );
use IO::Select;

my $threads = 4;
my $sel = IO::Select->new;
my %seldata;

my @name = ('read_genome', 'read_mapfile', 'read_GTF', 'read_RM');
my @task = (\&read_genome, \&read_mapfile, \&read_GTF, \&read_RM);
my %ret;

if ($threads == 1) {
  for my $id (0 .. $#task) {
    $ret{$id} = {};
    $ret{$id}{result} = eval { $task[$id]->() };
    $ret{$id}{error}  = $@;
  }
}
else {
  # start all forks
  for my $id (0 .. $#task) {
    if (open my $fh, '-|') {
      $sel->add($fh); # parent
      $seldata{$fh} = '';
    }
    else {
      my $data = {};  # child

      $data->{id}     = $id;
      $data->{result} = eval { $task[$id]->() };
      $data->{error}  = $@;

      print freeze $data;
      exit;
    }
  }
  # acquire data
  while ( $sel->count ) {
    for my $fh ( $sel->can_read ) {
      if ( 0 >= sysread $fh, $seldata{$fh},
           16 * 1024, length $seldata{$fh} ) {

        my $answer = thaw delete $seldata{$fh};
        $sel->remove($fh);

        $ret{ $answer->{id} } = {
          result => delete $answer->{result},
          error  => delete $answer->{error}
        };
      }
    }
  }
}

sub read_genome {
  # do something
  return { 'aa' => 'bb' };
}
sub read_mapfile {
  # do something
  return { 'cc' => 'dd' };
}
sub read_GTF {
  # do something
  die 'exception';
  return { 'ee' => 'ff' }; # not reached
}
sub read_RM {
  # do something
  return { 'gg' => 'hh' };
}

# use data generated in the subroutines

use Data::Dumper;

for my $id (0 .. $#task) {
  say "## ", $name[$id];
  if (length $ret{$id}{error}) {
    say "ERROR: ", $ret{$id}{error};
    next;
  }
  say Dumper($ret{$id}{result});
}
[download]

Output:

## read_genome
$VAR1 = {
          'aa' => 'bb'
        };

## read_mapfile
$VAR1 = {
          'cc' => 'dd'
        };

## read_GTF
ERROR: exception at j0.pl line 71.

## read_RM
$VAR1 = {
          'gg' => 'hh'
        };
[download]

Regards, Mario