I wonder if maybe there are some easter eggs hidden in perl?

I doubt it, but if so, they're hidden in plain sight: Perl source.

Despite its availability, nobody has ever accused the Perl source of being transparent and legible, though... ;)

Modules are a different story. Even core modules often have rich non-core histories before they're inducted into the Perl core distribution. Nevertheless, for the most part I think you would find them to be free from intentional surprises.