catenate

Unix fmt double-spaces after periods, except periods after single letters.
Of course, that's only useful to you if you compose text in a text editor,
and pipe it through fmt (or par, if you are that picky), before publishing it.

Thanks to HTML, however, you wouldn't know this text, for example,
had lines about 72 characters,¹ was carefully hand-justified after fmt(1)
to leave no dangling words alone on a line before or after punctuation,²
and had double spaces after all periods inside paragraphs, except T
and S in T. S. Eliot.