Mathematically, yes they are all the same.What is that supposed to mean? How do you "mathematically" compare programming languages (and yes I do know about denotational semantics)?
The point I was trying to make is that when you abstract away inessential syntactic differences then Perl, Ruby and Python are the same - and I still subscribe to that view.
During the history of computing several programming paradigms have evolved, so we have the imperative paradigm (the C family if you want), the functional paradigm with or without strong type-systems (Lisp, Haskell), the logical paradigm (Prolog) the OO-Paradigm (Eiffel) and of course all sorts of cross-breeds.
So if you look at the whole range of languages from assembler to C and C++, Lisp, Haskell, Prolog and so on the ecological niche of Perl, Python and Ruby is exactly the same - a few syntactical differences notwithstanding (and speed comparisons of concrete implementations are for this discussion entirely irrelevant).