Given an arbitrary LaTeX string... - which may contain 0 or more \parameter macros - of which each will either have one (\parameter{123}) or two (\parameter{1

Given an arbitrary LaTeX string... - which may contain 0 or more \parameter macros - of which each will either have one (\parameter{123}) or two (\parameter{123}{blue}) arguments ... besides regex, how else would you suggest replacing the entire macro with simply the value of its first argument (i.e. 123)? I can do it in one line with regex, but if there's an easier way, I'm all ears :)