IfDefinetags surround configuration directives that are applied if the "test" stated in the
IfDefinetag is true. The directives are ignored if the test is false.
The test in the
IfDefinetags is a parameter name (for example,
HAVE_PERL). If the parameter is defined, meaning that it is provided as an argument to the server's start-up command, then the test is true. In this case, when the Web server is started, the test is true and the directives contained in the
IfDefinetags are applied.