Free Hero Mesh

  no colums are fill width). The <format> is a string of exactly one or
  two characters; see the below list of possible formats. The <color> is
  the text colour, and is optional; it can be a number from 1 to 255, or
  it can be a sequence of parenthesized pairs of a number (-127 to +127)
  and colour, to mean use those colour if the value of this column is
  in range. It uses the colour for all values up to and including the
  specified number, so the numbers should be listed in ascending order,
  in order to work. If the last number is 127 then it is also use for all
  in order to work. The <string> is the heading; it is not allowed to
  higher numbers too. The <string> is the heading; it is not allowed to
  include control characters, nor can it include graphic characters with
  code number less than 32.

(<local> <type> <code...>)
  Defines a aggregate calculation. The <local> is the name of the aggregate
  to be referred by other blocks (which must start with a percentage sign,
  like a local variable does). The <type> is the type of aggregate, which

(right aligned) as signed decimal (d), hexadecimal (x/X), octal (o),
unsigned decimal (u). The ones with "0" will pad by 0 instead of spaces,
and the "d-" and "d+" will display a left aligned sign.

If a numeric format is specified but it is a text value, then it is treated
as "L" instead, unless format is "R*" in which case it is treated as "R".

(TODO: Mention valid instructions.)
Valid instructions in this block include:

 Arithmetic:  + - * ,* / ,/ mod ,mod Delta min ,min max ,max neg

 Bitwise:  band bor bxor bnot lsh rsh ,rsh

 Logical:  land lor lxor lnot

 Compare:  eq ne lt ,lt gt ,gt le ,le ge ,ge

 Misc:  Level _ in nin ret if else then

 Object:  Xloc Yloc Class Dir Misc1 Misc2 Misc3 Misc4 Misc5 Misc6 Misc7
   Temperature Density Player Input Bizarro CollisionLayers

Additionally, you can include numbers, strings (see below for their
meaning, which is different from the meaning in class codes), aggregate
names (with % at first), user flags (with ^ at first), class names, and
message names (both built-in messages and user messages are possible).
Accessing values of objects other than the current one is not possible.

(TODO: Usage of strings as instructions in this block.)