As others have said, the crypt is a "one way" function. Useful for passwords and such were you just want a yes/no answer of whether the encrypted version of what the user typed is the same as the stuff that is stored on the system (the password isn't stored as plain text).

If you want a 2-way function, then do a search on Perl Crypt and that will pop up a variety of options, like DES , PGP ( a public key scheme), blowfish, etc. there are a bunch...a whole bunch of options. Which one is best for you depends upon what you are trying to do. The point is that even though, crypt() is not it, there are many Perl modules that can provide this 2-way function.