Other people have suggested ways to do your tasks in parallel without overloading the processor(s), but perhaps you are asking the wrong question.

One also might ask why it takes 10 secs to validate a file? You can do a lot in 10 secs nowadays! 1000 files doesn't really sound a lot.

Why doesn't validation.pl handle a list of files anyway? i.e. so the command line accepts a list of files to be processed?

I'll also go out on a limb and suggest you're probably better not using bash at all, but modify validation.pl so it forks itself. I'm sure someone will say otherwise if this is a bad idea! :-)