I'm not sure how well it works for your specs, for example, it doesn't downgrade UTF-8 to its asciificated equivalents, but String::Dirify claims to come from the Movable Type codebase. I'm not aware of any other module and wrote my own ad-hoc solution, so if String::Dirify doesn't suit your needs, maybe writing your own module isn't that out of the question.

In reply to Re: RFC: Module to take a title and generate the core bit of the URL by Corion
in thread RFC: Module to take a title and generate the core bit of the URL by SilasTheMonk

Title:
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