Making Programs Faster

Mail Folder Analyzer Revisited

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The profiler says that main::letter_histogram is consuming most of the CPU time

     %Time ExclSec CumulS #Calls sec/call Csec/c  Name
      63.7   0.830  0.829    109   0.0076 0.0076  main::letter_histogram
      13.8   0.180  0.180      1   0.1800 0.1800  Mail::Util::read_mbox

A 20% speedup in this one function would reduce the program's run time by 1/8

     sub letter_histogram {
       my $strdex = (length $_[0])-1;
       $letter_hist{substr($_[0],$_,1)}++     for (0..$strdex);
     }

Not much to work with here
- I tried a bunch of things I thought of and some the test audiences suggested
- No luck
- Some of these things are in the Bonus Section at the end