Pfthb

Is it possible to reliably right-align the last word of a paragraph?

Using hfill works most of the time, looking like

Left stuff Right stuff.

but fails if the rest after hfill doesn't fit into the line. In that case the result looks like

Left stuff. Bla bla bla bla bla bla bla bla bla bla
bla bla bla bla bla bla bla bla bla bla bla
Right stuff.

but I want to get

Left stuff. Bla bla bla bla bla bla bla bla bla bla
bla bla bla bla bla bla bla bla bla bla bla
 Right stuff.

Actual example document

documentclass[12pt]article

begindocument

noindenttextbfIn real document, I would use textttstringhfill instead of textttstringhrulefill. The latter just demonstrates it better in an example document.

.

noindenttextbfThe command textttstringhfill is useful for aligning short text to left and right easily.

noindent Bla bla.
hrulefill Yada yada.

.

noindenttextbfIf the parts get too long, they are not correctly aligned.

noindent Bla Bla Bla Bla Bla Bla Bla Bla Bla Bla Bla.
hrulefill Yada Yada Yada Yada Yada Yada Yada Yada Yada.

.

noindenttextbfBoxes don't help.

noindent hboxBla Bla Bla Bla Bla Bla Bla Bla Bla Bla Bla.
hrulefill hboxYada Yada Yada Yada Yada Yada Yada Yada Yada.

.

noindenttextbfWhat I am actually trying to do.

noindent Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla 
hrulefill (statement:1)

.

noindent Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla Bla Bla
hrulefill (statement:1)

.

noindenttextbfAn approximation of what it should look like, if the last line before ``(statement:1)'' is full.

noindent Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla bla Bla Bla Bla
\.hrulefill (statement:1)


enddocument

There is a nice example in The TeXbook to do this. See chapter 14, page 106.

documentclassarticle
defsigned #1 (#2)unskipnobreakhfilpenalty50
 hskip2emhboxnobreakhfilsl#1/ rm(#2)
 parfillskip=0pt finalhyphendemerits=0 par
begindocument
hsize 9cm
This is a case where the name and address fit in nicely with the review.
signed A. Reviewer (Ann Arbor, Mich.)

But sometimes an extra line must be added. signed N. Bourbaki (Paris)
enddocument

You could make it a bit more standard for LaTeX:

documentclassarticle
newcommandsigned[1]%
 unskipnobreakhfilpenalty50
 hskip2emhboxnobreakhfil#1
 parfillskip=0pt finalhyphendemerits=0 par
begindocument
hsize 9cm
This is a case where the name and address fit in nicely with the review.
signedemphA. Reviewer (Ann Arbor, Mich.)

But sometimes an extra line must be added. signedemphN. Bourbaki (Paris)
enddocument

And the explanation of how it works from The TeXbook:

If a line break occurs at the penalty50, the hskip2em will disappear
and the empty hbox will occur at the beginning of a line, followed by
hfil glue. This yields two lines whose badness is zero; the first of
these lines is assessed a penalty of 50. But if no line break occurs
at the penalty50, there will be glue of 2 em plus 2 fil between the
review and the name; this yields one line of badness zero. TEX will
try both alternatives, to see which leads to the fewest total
demerits. The one-line solution will usually be preferred if it is
feasible.