Making Programs Faster

`Devel::DProf`

     %Time ExclSec CumulS #Calls sec/call Csec/c  Name
      30.1   2.149  2.125   4104   0.0005 0.0005  Mail::Header::_fold_line
      24.6   1.756  3.414   2052   0.0009 0.0017  Mail::Header::_fmt_line
      12.2   0.870  0.869    109   0.0080 0.0080  main::letter_histogram
      6.60   0.470  0.458   2052   0.0002 0.0002  Mail::Header::_insert
      5.77   0.411  4.275    109   0.0038 0.0392  Mail::Header::extract
      ...

About 30% of the program's total run time was spent inside Mail::Header::_fold_line
- Another 24% was spent in Mail::Header::_fmt_line
8 of the top 15 functions, totaling 82% of the run time, are in Mail::Header
Tentative conclusion: To make this program faster, get rid of Mail::Header