I have been searching everywhere in the emacs lisp documentation for how to regular expressions search into a string. All I find is how to do this in buffers.
Is there something I'm missing? Should I just spit my string into a temporary buffer and search for it there? Is this just the coding style of elisp, something I'll get used to? Is there a standard solution to this problem. Manipulating buffers seems cludgy when I should just be able to search straight into a variable already present.
Here is a discussion of string content vs buffer content in the Emacs wiki. Just store your string as a variable.
The tricky thing about strings is that you generally do not modify the string itself (except if you perform array functions on string, since a string is an array, but this should generally be avoided), but you return the modified string.
At any rate, here is an example of using a string in elisp.
This will trim the whitespace from the end of a string:
(setq test-str "abcdefg ")
(when (string-match "[ \t]*$" test-str)
(message (concat "[" (replace-match "" nil nil test-str) "]")))