Usage:
/SUB [OFF|ON|FULL]
Sets the flag %{sub}.
If the flag %{sub} is OFF (0), all lines except for history substitutions (line beginning with '^') and commands (/) are sent as-is to the socket.
If the flag %{sub} is ON (1), the sequences "%;" and "%\" are substituted with newlines, and the sequence "%%" is substituted with "%", and the sequence "\n" is substituted with the character with decimal ASCII code nn.
If the flag %{sub} is FULL, text is processed just as if it were the body of a macro (see "evaluation") called without any arguments. This allows you to have in-line macros in regular input.
The flag %{sub} defaults to 0 (off).
See: general, evaluation