ProLog is the one big language Perl did not (as far as I can see) borrow from, except for the customary extension .pl , which suggests that Larry Wall was not completely aware of the existence of ProLog at that time.
Some do not even consider ProLog a programming language. True: The prolog engine favours depth-first backtracking solutions and if your problem does not fit the prolog set of solutions that behaviour can get terribly in the way. But...
There are lots of partial problems where the prolog engine presents a very good fit. I like the elegant syntax, the expressive power and especially the way of thinking that comes with using it.
I have really tried to imagine ways I could combine Perl and Prolog, into some hybrid interpreter combining the niceties of both languages but I could not come up with feasible proposal, or even a readable piece of code that would demonstrate the huge power of that combination. Yet I am convinced that even Perl could gain expressive elegance and power by borrowing from Prolog. How? I don't know. Yet - I hope.
In reply to Re: Favorite programming language, other than Perl: