Originally Posted by corporate-wage-slave

I don't specifically know about TAP, but in broad aviation terms that would be an origin open jaw ticket, so it would be constructed by fusing two single tickets and charged accordingly, but may be some leniency on taxes and / or fees. There is a Maximum Permitted Mileage involved, and PTY to MEX would perhaps allow some extra leeway, but not a lot, usually it's about 20% extra miles allowed. That wouldn't get you to SCL.