Because you cannot have functions with dots in their names, so we need an alternative. This is needed because the syntax in vim for having multiple filtypes at once is by interspersing them with dots. So if I want a haskell file that is also a script file, I need to set the filetype to `haskell.script`. This way all the haskell filetype-specific things such as syntax highlighting and plugins still work, but I can disambiguate between `haskell` and `haskell.script` for the purpose of the vim-slime plugin.