The bifcl program simply takes a .bif file as input and generates C++
 header/source files along with a .bro script that all-together
 provide the declaration and implementation of Bro Built-In-Functions
 (BIFs), which can then be compiled and shipped as part of a Bro
 plugin.
 .
 A BIF allows one to write arbitrary C++ code and access it via a
 function call inside a Bro script. In this way, they can also be used
 to access parts of Bro's internal C++ API that aren't already exposed
 via their own BIFs.