The chop version is wrong, it's trimming chars from the end, but counting them from zero. This fixes that:

for( @data ) {                                 ## use $_ to alias the 
+lines
    my $p = length();                          ## Allow pre-decrement 
+and count backwards
    $freq{ chop() }[ --$p ] += $inc while $p;  ## implicit arg for cho
+p; avoid call to length.
}
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