Update: Don't use this. $1 comes from the previous match, not the current one. You would have to use experimental features for a solution in this vein.

This reads a little nicer, but I don't know whether you'd consider it cheating. It's a Perl regex: 

/^(\d{1,3})${\($1 > 255 ? qr(^) : qr($))}/

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Three digits, then interpolate a scalar ref block that tests what has already matched and returns the rest of the regexp: if the number is too high, the pattern is impossible; otherwise, end-of-string.

Update: meant to link to the post, not the poster. So now "solutions in this vein" links to the post.

Caution: Contents may have been coded under pressure.

In reply to Re: Regexp for range of numbers by Roy Johnson
in thread Regexp for range of numbers by loris

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