Re^2: Regexp for range of numbers

You don't need to test against zero. Or put anything in the success-pattern; an empty pattern matches just fine.

/^(\d{1,3})$(?(?{$1<256 }) | . )/x
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or you could move your anchor and use an impossible anchor for the fail-pattern:

/^(\d{1,3})(?(?{$1<256 }) $ | ^ )/x
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Caution: Contents may have been coded under pressure.

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Re^3: Regexp for range of numbers by Anonymous Monk on Apr 05, 2005 at 12:37 UTC
I tend to use `(?!)` for the always fail pattern (there are no positions that aren't followed by the empty string). `^` might match if a `/m` flag is in use, or if the zero-width assertion is done at the beginning of the string. An empty string works fine as an always match pattern - or `(?=)` if you want to go symmetric.	[reply] [d/l] [select]