The fec command works in the same way as fe, except that it iterates over each character rather than each word.
Leading whitespace between the opening parenthesis and first non-whitespace character and trailing whitespace between the final non-whitespace character and the closing parenthesis is ignored. This is probably not the ideal behavior, but it is backwards compatable.
The variable list that you pass to the fec command are local variables, and not global variables. These variables continue to be visible after the fec command finishes.