Tickets bought on-line for TER journeys in Occitanie between 15th and 24th September for journeys between 16th September and 30th November will be half price according to SNCF TER website. Tickets are for one way and not refundable nor changeable (though possibly could be given away or sold). The exercise is part of the Mobility Week, designed to encourage people to get about in the region.
Details are on the website at https://www.ter.sncf.com/occitanie/offres/tarifs/semaine-mobilite/%5Btab%5Dnotreoffre