Originally Posted by under the clocks
Can I depart my country of origin, and then on return, use my 4 segments?
Yes.
A problem that youre going to run into (potentially) is the GLA-DUB segment. Aer Lingus is the only carrier serving the route according to my information. Maybe they will remain in OW, however I highly doubt it. If they dont then you might run into some troubles down the line. You still have one more european segment so I would personally book gla-lon-dub.