=pod

=head1 NAME

playfair.pl - an encryption/decryption tool inspired by Dorothy Sayers.

=head1 Description

Encodes or decodes input according to the Playfair cipher, as described
in Dorothy Sayers' I<Have His Carcass>, among other places.  In accordance
with amateur cryptographic convention, ciphertext is printed in 5-character
uppercase groups, while decoded text is printed in lowercase 5-character
groups (whitespace and punctuation are lost in this process).

=head1 Usage

  playfair.pl [-o outfile] [-i infile] [-d | -e] [ keyword [infiles] ]