It is now possible to return a single filter from a filter file, e.g.
``` lua
-- Switch single- and double quotes
return {
Quoted = function (q)
elem.quotetype = elem.quotetype == 'SingleQuote'
and 'DoubleQuote' or 'SingleQuote'
return elem
end
}
The filter must not contain numerical indexes, or it might be treated as
a list of filters.