The "using" rule is a convenience rule:

 

using MODULE_NAME : field1 : field 2 : ... : field9 ;

 

The above essentially does this:

 

import MODULE_NAME ;

MODULE_NAME.init field1 : field2 : ... : field9 ;

 

So, if you look at the gcc.jam module, you'll notice that its init() rule's signature is this:

 

rule init ( version ? : command * : options * )

 

Thus, the using rule would be used like this:

 

using gcc : $(valid-gcc-module-version-string) : $(optional-command-to-gcc-exe) : $(options) ;

 

Where $(options) can be something like <root>root/directory or <flavor>mingw.

 

You can find the using() rule's definition in the toolset module.

 

Hope that helps,

Aaron