Secondly I suspect that the problem (at least for regex but maybe not for glob) is undecidable.

I don't think so, at least in the computer science sense of "undecidable". For every perl regex (that doesn't do evil stuff with code assertions) you can make it match any string with this transformation: 

m/($old_regex)?/

[download]

(Matches the empty string and thus every possible string).

Which is an edit distance of 3, if we count on a character base. So all you have to check is every possible regex with an edit distance of 1 or 2, which are still very many but finite. (Assuming this kind of transformation is actually allowed)

I don't know if that leads to any kind of practical solution though, and I don't know if OP actually talks about regexes or globs.

In reply to Re^2: Edit distance between regular expressions by moritz
in thread Edit distance between regular expression by future.open

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