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Help with regex  find captured pattern twiceby pachydermic (Beadle) 
on Apr 09, 2013 at 21:24 UTC ( #1027848=perlquestion: print w/replies, xml )  Need Help?? 
pachydermic has asked for the
wisdom of the Perl Monks concerning the following question:
Hey guys, my problem involves rewriting equations with regular expressions. I have a list of special "endogenous" variables which need to be changed from "x" to "xSS*exp(x)" everywhere they occur in an equation. I'm working with time series, so "x(1)" or "x(+1)" needs to be changed to "xSS*exp(x(1))" or "xSS*exp(x(+1))", as well.
For example, let's suppose that my endogenous variables are: y, c, k, a, and h.I need to take this: y = a*(k(1)ˆalpha)*(hˆ(1alpha));and turn it into this: (ySS*exp(y)) = (aSS*exp(a))*((kSS*exp(k(1)))ˆalpha)*((hSS*exp(h))ˆ(1alpha));Now I've already gotten started on this. Assume I already have a list of variables and equations to work with (contained in a single string which also has new lines). My code is:
And that's mostly okay except for the equation where you find "c/c(+1)" because the "/" character is already captured when the code finds "c/"  therefore "/c(+1)" isn't replaced. You can't just ignore the first (\W) because then parameters like "theta" would be problematic. I know my regexs aren't very good anyways, so I'd like some advice about how to handle this problem. Thank you very much for your time  hopefully I've explained everything clearly.
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