Emacs

The second bracket part of your regex just needs some additions: [a-zA-Z0-9-._] Basically add any additional characters at the end after the ranges.

Elisp regular expressions are case insensitive by default, so they should match uppercase letters too.

To just add a dash, you could simply put that into the second group. So [a-z0-9-], you don’t have to escape it because it can’t be a range operator if it’s at the end of the group. The same goes for any other character you want to match.

You could also use [\\w. _-] (notice the literal space between the dot and the underscore). The \w is a shorthand for A-Za-z0-9. This should match all valid filenames as long as they don’t contain letters with diacritics.

On a POSIX filesystem (MacOS, Linux, BSD, etc.), any character except '/' can be part of a filename. So why are you limiting yourself to a couple of punctuation characters? The best regex to match filenames is: "[^/]+"

If you're using Windows, it gets a bit trickier, but for reading the filesystem, "[^/\\\\]+" seems like it should be adequate. If you want to make sure you can create a filename on Windows, you'd have to exclude a few more characters. Nevertheless, excluding invalid characters still seems like a better approach than trying to include all the valid ones.