A file needs to know it's place in the world

Yes. See this forum thread - essentially using get_filename(piport) in your script. Well, that's returning the filename being read - from which you could of course determine the containing directory. That thread also talks about being able to do it inside a function defined within a SKILL file (rather than defining a global variable to determine where the file is) - which wasn't documented at the time. It is now documented in the SKILL Language User Guide, in a section headed "Read-time Evaluation" which says:

Read-time Evaluation

SKILL provides the read-time eval operator #. for evaluating expressions at read-time.
When this operator is encountered, the expression following the dot is evaluated and the
result of this evaluation replaces the #. For example, in the code below
get_filename(piport) is evaluated at read-time and the results are inserted when the
entire expression is compiled:

procedure(printFileThisWasFrom()
  printf( "The file is:%s\n" #.get_filename(piport) )
)

If this function was defined within a file "code.il" then after the read-time evaluation, the
expression would expand to the following, before being passed to the SKILL evaluator:

procedure(printFileThisWasFrom()
  printf( "The file is:%s\n" "code.il" )
)

Regards,

Andrew

As always - thanks for your swift and perfect response!