Alas, I can't answer your questions. =( TedPride came up with something useful; I have this vague thought to contribute:

If the system calls  egrep,  it will spend resources on  forking which might well compete with the load that egrep would do on the machine. -- So if you're going to rewrite the process of spawning the egrep, consider rewriting it to use a single call to  perl  to do all the greping?

Cheers, Sören