Very interesting!

So, the meaning of -p is performed by textually including the loop around the actual code, so beginning with "}" will close the -p's while loop, and the final "{" will ballance the closing brace at the end of the expansion.

I never thought about that. I always just figured that built-in looping construct was done on a syntactic boundary, like:

while (<>) {
   eval $option_e;
   print
   }
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only done in the parse-tree level, not by simply generating more source text!

So... that's not documented or to be relied on, right?

—John