use the following to process this file:
  m8 hello.m8

using the 'def' macro
usage: def name body
use 'def' to define a new macro called 'name' that returns 'octobanana'

[M8[ def name octobanana ]8M]

use the new macro 'name' to insert the defined value
hello, [M8[ name ]8M]!

using the 'def' macro overload
usage: def name 'info' 'regex' body
use 'def' to define a new macro called 'hello'
set its usage description to 'name'
set its argument regex to '(\w+)'
  '(\w+)' match a single word
  '()' denotes a capture group
  '\w' matches a word character
  '+' is a quantifier of one or more
set the templated return body to 'hello, {1}!'
  where '{}' denotes a template parameter
  '{0}' contains the full regex match
  '{1}' contains the first capture group match

[M8[ def hello 'str' '(\w+)'
hello, {1}!
]8M]

use the new macro 'hello' passing the 'name' macro as an argument
[M8[ hello [M8[ name ]8M] ]8M]