Set in typewriter font; equivalent to `\mbox{\tt #1}', except that the argument can include any old printable ASCII characters, including properly-nested braces (escaping them is irrelevant). If you want to do something weird, do it another way. Note that linebreaks within the `\tr' are prevented.

The equivalent non-typewriter thing is `\pl'.

APRIL91: see section See diff-fonts-in-text for further comment on this stuff.