Improvements to tackle wrong expression outputs - rebase from #605

[mmatera]

[mmatera]

@rocky, what I did here is to merge #605 successively with all the releases after its creation (v1.0, 1.1.0, 1.1.1, 2.0.0, 2.1.0, and master). Then I create a new branch over master, and copy the files that changed from that merge. Now I am trying to make this pass the tests. And afterwards, we need to see if all this work was useful...