Various perl scripts are used in the make system.
This is called by the top level makefile to create a new configuration or to modify an old one. It parses an options file setting environment variables as specified in that file, and then runs the autoconf-generated configure script.
This file is called from the configure script to determine the way Fortran names are represented for the specified Fortran compiler. It works out the names for subroutines/functions, and for common blocks, and writes a perl script which can be used to convert a name to the appropriate form so C and Fortran can be linked together.
This generates the skeleton for a new thorn.