o<mychange> sub
   o10 if [#<_current_tool> NE #<_selected_tool>]
      ;(DEBUG, current tool: #<_current_tool>, selected_tool: #<_selected_tool>)
      #<saved_z> = [#<_z>]      ; save position
      #4999 = #<_selected_tool> ; store selected tool to use M61 at start-up
      G53 G0 Z87     ; rapid to tool change location
      M6
      ;G53 G0 Z50
      ;M101          ; engage spindle air blower
      ;G53 G0 Z35
      ;M102          ; disengage spindle air blower
      ;(DEBUG, saved-z: #<saved_z>)
      G43
      G0 Z[#<saved_z>] ; restore position
   o10 else
      (DEBUG, tool #<_selected_tool> already in spindle)
   o10 endif
o<mychange> endsub
M2