Win32::Process::Info can help in this case. The result is an AoH. Each hash contains info of a process. There are lots of information, and those three pieces are particually helpful to you: ProcessId, ParentProcessId and CommandLine (or Caption). You can find the child process's processid either base on CommandLine/Caption or ParentProcessId.

use Win32::Process::Info;
use Win32::Process;
use Data::Dumper;

use strict;
use warnings;

my $pi = Win32::Process::Info->new();
my @info = $pi->GetProcInfo ();   
print Dumper(\@info);
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