.TP
cmdchar ['\fIone-byte-char\fP']
The default command-introduction character is a space, but it may be
changed via this command. The single quotes surrounding the character
are required. If no argument is given, the current value is printed.

An input line consisting of a single question mark will also print the
current value (useful for when you don't know the current value).

Woe to the one that sets the command-introduction character to one
of the other special input-line characters,
such as\&\&+\&\&,\&\&/\&\&, etc.