There are five (5) types of configuration directives used with Kamailio.

1. C-Style Control Directives
2. Apache Name/Value Pairs
3. Normal Name/Value Pairs
4. Modify Parameter Procedure
5. Route Functions

Configuration file comments are PHP style, without the double-slash line comment. Only hash (#) will work for line comments.
This gets confusing since the hash-bang (#!) is used at the beginning of the C-Style Control Directives.

/* block comment
   block comment */
// this is NOT a line comment
# this is a line comment
#!c_style_directive

The semicolon works with all forms of configuration directives as an instruction separator. Allowing for comments or additional configuration directives on the same line.

configuration_directive_a; configuration_directive_b
configuration_directive; # comment about the configuration directive

Available directives:

  #!define NAME - define a keyword
  #!define NAME VALUE - define a keyword with value
  #!ifdef NAME - check if a keyword is defined
  #!ifndef - check if a keyword is not defined
  #!else - swtich to false branch of ifdef/ifndef region
  #!endif - end ifdef/ifndef region
  #!trydef - add a define if not already defined
  #!redefine - force redefinition even if already defined
  #!subst
  #!substdef

(delimited by a space, value within quotes)

(delimited by an equals sign)