Documentation can be found at http://tcllib.sourceforge.net/doc/md5crypt.html
(at least it will be the next time it's regenerated).
This package provides an implementation of the MD5-crypt password encryption algorithm as pioneered by FreeBSD and currently in use as a replacement for the unix crypt(3) function in many modern systems. An implementation of the closely related Apache MD5-crypt is also available.
The output of these commands are compatible with the BSD and OpenSSL implementation of md5crypt and the Apache 2 htpasswd program.
Example
% md5crypt::md5crypt password 01234567 $1$01234567$b5lh2mHyD2PdJjFfALlEz1 % md5crypt::aprcrypt password 01234567 $apr1$01234567$IXBaQywhAhc0d75ZbaSDp/