urlregexpmapping with ant task

Using xmlc ant task, I am trying to replace all urls with ../ to be ../sec/ and 
all ../../ urls to be ../ . To do this I am using the following args:

-urlregexpmapping \.\./(?!\.\./) ../sec/
-urlregexpmapping \.\./\.\./ ../

When using the above args, I get gnu.regexp.REException: quantifier (?*+{}) 
without preceding token. 

Does anyone have an idea of why this is happening? Are regexp look aheads 
allowed?

Thanks,

Kyle


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