Use display instead of print.

The procedure 'display' is defined in R5RS whereas 'print' is not, so using display will help to achieve a greater degree of portability between Scheme implementations.
Added help message.

The command 'hog help' has been implemented to display a help message. A lambda function is called that really does nothing but return the help string. It could also have been implemented with a simple define instead of a lambda, but the implementation may change in the future such that use of a lambda is preferred.
Clarified cmd-help comment.

Since cmd-help is defined as a procedure that returns a help string rather then print it, the comment was edited to document cmd-help more accurately, as opposed to it being a function that actually prints the string.