I'm sure I read somewhere that OO in Perl can slow down compilation and execution time by upto 40%... is that right?

Sure, somewhere in a Java or Python forum ... ;-)

OOP has a little overhead, but 40% looks like a very constructed example. And "up to 40%" could also mean zero. If you want to know, run benchmarks.

If you want to know why your code is slow, use Devel::NYTProf.

Alexander