Assigning to a hash using %this_hash = ... always overwrites the entire hash.

Additionally, the code of:

/^(\d+)\W\d+\W\d+\W(\d+)\W\w+/; 
$CpmRC{$1}=$2;
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is dangerous, because when the match fails, you get the previous value of $1 and friends. Always do this in the conditional based on the match:

if (/^(\d+)\W\d+\W\d+\W(\d+)\W\w+/) {
  $CpmRC{$1}=$2;
}
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-- Randal L. Schwartz, Perl hacker