Subroutines Search Order

1. Main program file.
2. In the same directory as the main program file (side by side).
3. Profile directory's UserSubroutines directory (if it exists).
4. Profile directory's Subroutines directory (if it exists).
5. Mach installation directory's Subroutines directory.

If the sub file name is given in the M98 line comment:

1. Profile directory's UserSubroutines directory (if it exists).
2. Profile directory's Subroutines directory (if it exists).
3. Mach installation directory's Subroutines directory.

It will also search all of the file extensions if the filename doesn't have an extension.