MD5 is known to have clashes (duplicate hashes for different input).

http://www.ssh.com/tech/crypto/algorithms.html

http://www.tml.hut.fi/Opinnot/Tik-110.501/1995/practical-crypto.html

Of course quantum computers will make all of this moot ;-) (/me ducks)

--
perl -pe "s/\b;([st])/'\1/mg"