|Pathologically Eclectic Rubbish Lister|
positive look behind regexp mysteryby rovf (Priest)
|on Aug 01, 2008 at 08:17 UTC||Need Help??|
rovf has asked for the wisdom of the Perl Monks concerning the following question:
I wanted to substitute the extension of a filename by 'txt', that is to transform abc/xyz.something into abc/xyz.txt. This is easy, but maybe driven by the sudden thought that I'm becoming an old man as the years passed by without ever having tried a positive look behind regexp, I came up with the following silly solution:
That is, substitute the longest string at the end of the filename which does not contain a period, but is preceded with one. Interestingly, this did not work - no substitution was taking place.
In my case this is overkill, because I happen to know in my filename that there *is* a period, so I could have much easier written
(this would however replace the complete filename with txt if it doesn't contain a period).
Nevertheless I would like to know *why* my original solution has failed. Any suggestions?
Ronald Fischer <email@example.com>