Format strings are used for prompts, but can also be used directly using the control-format control on any handle that supports output. No tailing new line is added, so it needs to be added manually if required.

  538 (* 0) "cat" ~> control %stdout sni:73 "The current tag is: $*\n"
The current tag is:   538 (* 0) "cat"
  538 (* 0) "cat" ~>
                

Currently, the following variables are supported in prompts:

$A

&

$B

|

$C

(

$E

$F

)

$G

>

$H

$L

<

$Q

=

$S

$$

$

$_

$*

  538 (* 0) "cat"

$:

<none> 

$R

$P

$.

$*

  538 (* 0) "cat"

$D

$T

$V

$N

$+

$M