.so ul.tmac
.nr xxx \n[.ps]s
.tm .ps \n[.ps]; xxx \n[xxx]
.ll 5i
.in 1i
.ti 2i
.Underline This is a test of the .Underline macro. \
  As you can see, it works across lines without problems.
.Underline Note, however, that you need groff version \
  1.19.1 to get correct spacing right after a \
  period -- in older versions of groff, the `\[rs]?' \
  escape wasn't transparent with respect to \
  end-of-sentence recognition.
It works also across page breaks, and it isn't affected by
vertical position traps.
'in .5i
'll -.5i
.Underline Consequently, it can be used with all macro packages, \
  provided it doesn't use the diversion trap.
Actually, none of the macro packages which are distributed with
groff use it.

The
.Underline line length
and
.Underline indentation
can be changed without
.Underline any restriction;
I think that such a macro has many applications.
