On a side note, the error checks you do on the CONFIG filehandle as you read it in are already done by perl automagically.

#The line:
while ( defined ($_ =  <CONFIG>) )

#can be simplified to:
while(<CONFIG>)
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When you use the <> in the conditional of a while loop, perl automatically sets the $_ variable to be the input record it read from the file. It also checks that it is defined() for you so you don't have to.

Just a little sweet syntactic sugar for you.