RFE: would be nice to have richer, regex()-like file search (beyond just glob)

[noblem]

In issue #89 I mentioned a use case of wanting to get a list of 3 kinds of files in a directory

*.png
*.txt
*.html

and store this list into a single output variable. The glob() function is not expressive enough to generate such a list with a single call, but a regular expression-based function would be.