using regex to not match a string

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to write a program to match all occurences of &, but not any of &

I have been able to generate &[^amp;] for my patern, but this negates matching on &a, &m, &p, &; which I would like to find.... I tried &[^a][^m][^p][^;], but that still blocks &a

How on earth do I do this?

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Re: using regex to not match a string by Tanktalus (Canon) on Apr 18, 2005 at 23:52 UTC
[...] is a character class. You want (?!...) (see perlre). e.g., `/&(?!amp;)/` Update: Darn. Too slow. :-) (Although I got the semicolon ;->)	[reply] [d/l]
Re: using regex to not match a string by tlm (Prior) on Apr 18, 2005 at 23:51 UTC
Oops. Didn't notice the `;` at the end of the pattern you want to avoid. What Tanktalus said: `/&(?!amp;)/` . `/&(?!amp\b)/` [download] The above will match `&`, `&foo`, `&ersand`, but not `&` followed by a `\W` character or by the end of the string. If you don't want to match `&`, irrespective of what follows it, then use `/&(?!amp)/` [download] See `?!` in `perlre`. the lowliest monk	[reply] [d/l] [select]