You'll need to show us some example lines/records from your $genpept file to clarify what you are trying to achieve. Your code looks wrong on a number of levels. For example, you're opening the file but not actually reading from it (or even checking that the open succeeded). Also, the quoting around $genpept in open(my $in,"$genpept") is pointless.

If you want to slurp the whole file into the $in variable, you need something like:

open(my $fhin, '<', $genpept) or die "open '$genpept': $!";
undef $/;
my $in = <$fhin>;
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Alternatively, if the file consists of multiple lines, it seems better to not slurp the whole file, but to read it line by line:

while (my $in = <$fhin>) {
   # ... split etc. done once for each line $in.
}
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