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Re: A Regex simple Question

by Sidhekin (Priest)
on Sep 06, 2007 at 15:54 UTC ( #637464=note: print w/ replies, xml ) Need Help??


in reply to A Regex simple Question

Negative lookahead is always tricky ... you're on the right track though.

In this specific case you could do this:

/^a(?!b)(?:(?!ab).)+b$/

... or even this:

/^(?!.*ab)a.+b$/

... unless I've read you wrong, and you want to allow the string "ab" and even "ab000b"/"a000ab" (since the "ab" is not strictly between the "a" and the "b"), in which case you want this:

/^a(?:(?!ab.).)*b$/

... or even this:

/^(?!.+ab.)a.*b$/

Always tricky, the negative lookahead ... if you can split it, like FunkyMonk suggests (or some variation thereof), it'll be far more readable.

print "Just another Perl ${\(trickster and hacker)},"
The Sidhekin proves Sidhe did it!


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