This module provides a case preserving but case insensitive hash.
This means that
 
    $cphash{KEY}    $cphash{key}
    $cphash{Key}    $cphash{keY}
 
all refer to the same entry.  Also, the hash remembers which form of
the key was last used to store the entry.  The `keys' and `each'
functions will return the key that was used to set the value.