I'd be pretty happy to recommend apache as well, straight off the rank...however if you have specific needs you need addressed, you might better qualify what "best" entails for you.
If you don't have software install rights OR you have IIS already installed and not much idea about web stuff and more importantly apache, then a little script or two might as well just run from IIS. I'd push stronger for apache if more substantial perl CGI programs are run, and people at work rely on the perl CGI(s), e.g. stability, performance, flexibility, and maintenance. Then again you may balk at the learning curve for apache config.