== !BeginIf / !EndIf
Encloses directives that will be processed only if a test is true at startup.
This is equivalent to {{{ httpd }}}'s {{{ IfDefined }}}

{{{
BeginIf Defined 
    ForceLog "defined"
EndIf
}}}

== !BeginIfNot / !EndIfNot
Same as above for false values.
This is equivalent to {{{ httpd's }}} {{{ IfDefined !parameter-name }}}

{{{
BeginIfNot Defined test
   ForceLog "not defined"
EndIfNot
}}}