Sane version of the perl code at at https://www.miek.nl/go/#processes

learning-go-pid-count.pl

#!/usr/bin/env perl
use strict;
use warnings;

# %child key = parent PID, value = array of child PIDs
use vars qw(%child $pid $parent);

open(FH, "ps -axe -o pid,ppid,comm |") or die;
while(<FH>) {
  s/^\s+//g;                                 # Remove any spaces at the beginning of the line
  tr/ / /s;                                  # Turn sequential spaces into a single space ("squeeze")
  next if /^PID/;                            # Skip ps output header
  ($pid, $parent) = (split(/ /, $_))[0,1];   # Space-delimited output; we only care about the first 2 fields
  push @{ $child{$parent} }, $pid;           # Append to the array
}
close(FH);

foreach $pid (sort { $a <=> $b } keys %child) {
  my $count = scalar @{ $child{$pid} };

  printf "Pid %u has %u child%s: [%s]\n",
    $pid,
    $count,
    ($count > 1 ? "ren" : ""),
    join(" ", @{ $child{$pid} });
}