Tybalt89's solution is neat. Here is a variation using MCE::Channel where the child sends the status to the manager process. The manager does a non-blocking read in the event the child crashed or exited early; e.g. not send the status.

MCE::Channel

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11150996
use warnings;
use MCE::Channel;

my @testLists = 1 .. 7; # FAKE for testing
my $opts = 'opts'; # FAKE for testing
my %pids; # NOTE changed to hash because children finish in any order
my $status = 0;

my $chnl = MCE::Channel->new();

foreach my $list (@testLists) 
  {
  while( keys %pids >= 2 )
    {
    delete $pids{ +wait };
    my $val = $chnl->recv_nb();
    $status += $val if defined($val);
    }
  if( my $pid = fork )
    {
    $pids{ $pid }++;
    }
  elsif( defined $pid )
    {
    my $status = regressions($opts, $list);
    $chnl->send($status);
    exit;
    }
  else
    {
    die "fork failed $!";
    }
  }
foreach my $pid ( keys %pids ) 
  {
  waitpid($pid, 0);
  my $val = $chnl->recv_nb();
  $status += $val if defined($val);
  }

print "status: $status\n";

sub regressions # FIXME for testing
  {
  print time, " pid $$ starting on (@_)\n";
  sleep 1 + int rand 3;
  print time, " pid $$ ending on (@_)\n";
  return 1;
  }

__END__
1678939864 pid 27850 starting on (opts 1)
1678939864 pid 27851 starting on (opts 2)
1678939866 pid 27851 ending on (opts 2)
1678939866 pid 27852 starting on (opts 3)
1678939867 pid 27850 ending on (opts 1)
1678939867 pid 27853 starting on (opts 4)
1678939868 pid 27853 ending on (opts 4)
1678939868 pid 27854 starting on (opts 5)
1678939869 pid 27852 ending on (opts 3)
1678939869 pid 27855 starting on (opts 6)
1678939871 pid 27855 ending on (opts 6)
1678939871 pid 27854 ending on (opts 5)
1678939871 pid 27856 starting on (opts 7)
1678939872 pid 27856 ending on (opts 7)
status: 7
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