Rather than using a regular expression, it's probably better to use the existing code base to do your job for you. In this case, the core module File::Spec can parse the path for you using the splitpath method.

However, if there's a good reason to do it with a regular expression, you can use:

/([^\\]*)$/

which will match and extract all the characters between the last backslash and the end of the string. Note this will fail on to do what you want on non-MS systems. See perlretut for more regular expression information.