FWIW, I agree. So while I had ++'d it, I wanted to offer another solution to the OP. As I get older, and probably more cynical, I worry about writing code solutions to problems that can be solved with trivial to implement unix solutions (i.e. I see unix tools as old CPAN modules that still work well).

I'm not saying that new code is bad, but just that in these types of cases there needs to be a significant advantage in writing code by hand since there is additional brainpower invested (esp. over time) into the solution. Perhaps your solution will significantly outperform the shell script solution for really large files, in that case the extra maintenance cost might be worth it for some.

Update:Minor format fix.