One option could be to have ${filename} only include the name until the first . and ${extname} could include everything after.
So for foo.blade.php:

• ${filename}: foo
• ${extname}: blade.php

Another option could be to have ${filename} only include the name until the first . and ${extname} include only the last extension. This would still allow users to add rules to cover the cases with the double extensions and I would assume users do not have many different combinations of double extensions that they work with so it wouldn't be to cumbersome to add.
So for foo.blade.php:

• ${filename}: foo
• ${extname}: php

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Happy Coding!

It might be a little unconventional, but I made a pull request for it, before it has been voted in, in which I added a template variable called filenamePart which accepts a number and returns the nth part of the filename including the extension separated by ., for example a.b.c.d with the pattern "${filenamePart(1)}-${filenamePart(2)}-${filenamePart(3)}-${filenamePart(4)}" would become a-b-c-d
#213033