Here's a way that avoids (for no particular good reason ) writing disk files by using perl's forked open. It also avoids eval (for maybe slightly better reasons ).

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1197603

use strict;
use warnings;
use Data::Dumper;
use Storable qw( freeze thaw );
use IO::Select;

my $sel = IO::Select->new;
my %returndata;

# this way you don't need to do an eval
my @subs = (\&read_genome, \&read_mapfile, \&read_GTF, \&read_RM);

for my $sub (@subs) # start all forks
  {
  if(open my $fh, '-|')
    {
    $sel->add($fh);
    $returndata{$fh} = '';
    }
  else # child
    {
    print freeze $sub->();
    exit;
    }
  }

while( $sel->count ) # get return data
  {
  for my $fh ( $sel->can_read )
    {
    if( 0 >= sysread $fh, $returndata{$fh},
      16 * 1024, length $returndata{$fh} )
      {
      my $answer = thaw delete $returndata{$fh};
      $sel->remove($fh);

      print Dumper $answer; # or whatever you want to do with it
      }
    }
  }

sub read_genome
    {
    # do something
    select undef, undef, undef, .1 + rand 1; # simulate processing tim
+e
    return { from => 'read_genome', results => { 1..4} };
    }
sub read_mapfile
    {
    # do something
    select undef, undef, undef, .1 + rand 1; # simulate processing tim
+e
    return { from => 'read_mapfile', results => { 5..8} };
    }
sub read_GTF
    {
    # do something
    select undef, undef, undef, .1 + rand 1; # simulate processing tim
+e
    return { from => 'read_GTF', results => { 1..10} };
    }
sub read_RM
    {
    # do something
    select undef, undef, undef, .1 + rand 1; # simulate processing tim
+e
    return { from => 'read_RM', results => { 2..5} };
    }
[download]

Prints (in a different order each time it's run)

$VAR1 = {
          'results' => {
                         '2' => 3,
                         '4' => 5
                       },
          'from' => 'read_RM'
        };
$VAR1 = {
          'results' => {
                         '5' => 6,
                         '1' => 2,
                         '9' => 10,
                         '7' => 8,
                         '3' => 4
                       },
          'from' => 'read_GTF'
        };
$VAR1 = {
          'from' => 'read_genome',
          'results' => {
                         '3' => 4,
                         '1' => 2
                       }
        };
$VAR1 = {
          'from' => 'read_mapfile',
          'results' => {
                         '7' => 8,
                         '5' => 6
                       }
        };
[download]