An SPL file contains literal text to output, interspersed with code generator instructions.
Code generator instructions are enclosed in square brackets '[' and ']'. Multiple statements can be included in a bracket pair. Additional statements have to be separated by a new line or a colon ':'.
Valid examples are:
[$x = 42
$x = $x + 1]
[$x = 42: $x = $x + 1]
Text not enclosed by [ and ], is written directly to the current output file.
To output literal square brackets, escape them with a backslash: \[ and \]; to output a backslash use \\.
Comments inside an instruction block always begin with a ' character, and terminate on the next line, or at a block close character ].