How to do equivalent of /(regexp){0}/ ?


 
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# 1  
Old 08-02-2011
How to do equivalent of /(regexp){0}/ ?

I don't want to have to resort to
Code:
 
/([^s][^t][^r][^i][^n][^g])/

though that does work.

Effectively, I need to be able to implement
Code:
 
/(?:(?:regexp1){0}[^-0-9])(regexp2)\D/

to basically match regexp2 as long as it is present and regexp1 is NOT.

So, how to do
Code:
 
/(regexp){0}/

?
# 2  
Old 08-03-2011
You need a zero-width negative look-behind assertion from the extended patterns. Example:
Code:
$ cat /tmp/test.txt
This should be matched.
This should not be matched.
$ perl -ne 'print if /(?<!not\s)be/;' /tmp/test.txt
This should be matched.
$

This User Gave Thanks to pludi For This Post:
# 3  
Old 08-03-2011
That's what I get for not reading the entire perlre doc. Smilie
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