Need example of HMAC SHA

[Heather Shaw]

I am a newbie to the gnupg software and am needing to
utilize the HMAC/SHA features of the libcrypt package.
Does someone have a quick & dirty example of this. 
Most of the examples I have found use the AES cipher
and in looking through the documentation, I have been
confused on how to implement the HMAC/SHA.  I am
trying to just encrypt/decrypt a basic string. 

Thanks for the help
~heather