If you're going to do this in shell, then you can avoid a bit of work: 

$ echo lbn9.pd.cnt | cut -d. -f1,3
lbn9.cnt

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However, since I think you're advocating writing the above in perl (with the backticks), it seems kind of redundant: 
join '.', (split '.', $name)[0,2]

[download]
which avoids all the overhead of forking and execing multiple (2-3) subprocesses. Personally, I find the backticks (or even system in general) to be vastly overused in perl, mostly by people pretending it's the shell rather than using it as perl.

In reply to Re^2: renaming files question by Tanktalus
in thread renaming files question by Angharad

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