The %--with% configure option is used to enable extensions that require external libraries. %--with% takes the installation prefix for that library as an optional argument. The %<with>% tag takes three attributes:

%name=% for the actual name of the "with" option

%testfile% for the relative path of a file to check for while running the configure script

a list of default paths to check

%name% and %defaults% are set to the extension base name and "%/usr:/usr/local%" if no values are given. The testfile attribute is mandatory. Textual data enclosed by the %<with>% is used to describe the "with" option in the output of configure --help calls.