> The rules are:
> 
> 1. Either a space or a tab delimit the initial macro on a line.
>    If the delimiter is a tab, that tab is lost.
> 
>    Examples:
>    .Fl<space>Fl       ->  Fl() Fl()  ->  "--"
>    .Fl<tab>Fl         ->  Fl() Fl()  ->  "--"
>    .Fl<tab><space>Fl  ->  Fl() Fl()  ->  "--"
> 
>    In this respect, there is a bug in mandoc.
>    A tab character does not delimit the initial macro on a line,
>    but .Fl<tab> gives you:
>    ERROR: bad character  <-- that's the tab
>    ERROR: unknown macro will be lost: unknown macro: Fl<tab>

Ingo,

Does the enclosed patch solve this behaviour?  I've enclosed a handy 
test as well.

Kristaps