This is a fixup for commit 3aded8e0.

':' is too common; it can be used in the filename.

This is a fixup for commit a73f5fea.

Note: fixers -> fixes, because of how test's `fixer_pkg` works.

This way, the ',' behaves like the old '/'. This change is introduced to
support division on multiple lines.

This id is a unique number that distinguishes callers from the same line.