apache cgi-scripts calling mail function, pstree ppid question

Hi folks
I've given myself a nice little exercise to help renovate
some very rusty basic C- skills.

Scenario:
one machine running apache with perl/cgi scripts and php
scripts calling the mail function. (qmail)
some of these scripts are being abused by spammers.

Goal: To play with qmail code so the X-headers show the uid
of the calling script's owner and the name of the script itself.
The plan is to traverse the pstree using
/proc/(pidno)/status to get ppids and prog names.
I realise I may have to move a way back up the tree to the
apache process and then back down thru that process to find
other processes it is running (including the calling script)...

....However: I have noticed when running pstree, I see

---httpd--mailer.cgi

and I see lots of
---qmail-inject --- qmail-queue

and so on, but I never see the tree showing the
mailer.cgi script or even its apache process as the parent
of the qmail-inject (or sendmail) progs.

What is the mechanism by which a php or perl script calls
the mail function without appearing as the mail function's
parent?

It is possible that someone could save me a lot of wasted
time and effort here. I like the challenge, but I'd like a
chance of at least partial success.

If a run a snapshot of the process table at the time the
mail is being inject, will I ever see any link between the
injction process and the "calling" script?


Thanks
ppl

Andy