Consider Proc::ProcessTable. You may want to look into porting that to any unsupported OS ...

use strict;
use Proc::ProcessTable;


my $tgt = shift || $$;
my %cmd;
my %children;
my $pt = new Proc::ProcessTable or die("No process table ");

sub
treeprint
{
   my ($pid, $indent) = @_;
   print ' ' x $indent,"$pid: $cmd{$pid}\n";
   # What the heck ... let's recurse to the end of the tree
   foreach (@{$children{$pid}})
   {
      &treeprint($_, $indent+1);
   }
}

foreach my $proc ( @{$pt->table} )
{
   push @{$children{$proc->ppid}}, $proc->pid;
   $cmd{$proc->pid} = $proc->cmndline;
}

&treeprint($tgt,0);
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