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There isn't that much context; it is in a subroutine, and sqr and piece are 'my' variables, which should pretty much decouple it from the remaining code:

sub GetSquares toshuffle:
  my sqr piece;
  // determine the squares the pieces in the given set are on.
  // the result is left in 3 global arrays:
  set left array;  // on left board half
  set light array; // as well as sorted by shade
  set dark array;
printr $space;
  for (sqr, piece) $space:
print . iter . #piece #sqr;
    if match #piece #toshuffle:
      if < * 2 file #sqr lastfile:  // left half
        push left #sqr;
      endif;
      if & 1 + file #sqr rank #sqr: // distinguish by shade
        push dark #sqr;
      else:
        push light #sqr;
      endif;
    endif;
  next;
print "got it";
endsub;

This routine is in the shuffle.txt file included in the preset Aurelian posted the link to 5 postings ago in this subject thread. That preset calls the routine ShuffleSetup (at the very bottom of the Pre-Game section), which eventually calls this routine. If you click that link it directly tries to execute the preset, which immediately exits after printing the $space array, and "iter0". It never gets to the "got it".