How to match all words but one?

Question

I'm trying to match expressions that start with PRE and end with PRE. I'm looking for a lazy match, that is the ending PRE in the matched expression should be the first one found after the starting PRE. I was trying to achieve this with a negative lookahead regex, testing on RegExr:

Regex:

PRE(\w|\s)+(?!PRE)

Expression to match:

PRE erp PRE edas PRE

The expression above is matched in full by the given regex, while I had expected only to match PRE erp PRE. Please suggest a regex that lazily matches expression starting and ending with PRE.

Answer 1

"(PRE)(.*?)(PRE)" 

This works for me in my (C#) code, returning one match, PRE erp PRE.

        var codeBlocks = Regex.Matches("PRE erp PRE edas PRE", "(PRE)(.*?)(PRE)", RegexOptions.IgnoreCase | RegexOptions.Singleline);
        MessageBox.Show("Matches found: " + codeBlocks.Count.ToString() + "\nMatch: " + codeBlocks[0].Value);

Answer 2

Supposed your language support lazy matching (if it supports look-around, I suppose it also supports lazy quantifier):

PRE(.*?)PRE

As this answer may be wrong, please specify your language next time. Regex has different set of features for different the languages.

Answer 3

This should do the job:

(?<=PRE)(.+?)(?=PRE)

http://regexr.com?31bc5