The Scarlets had their pride dented as Leinster, rival candidates for the PRO12 play-off spots, grabbed a bonus point in a 32-5 victory in Dublin.
The hosts scored tries through Andrew Goodman, Aaron Dundon, Jordi Murphy and John Cooney.
Andy Fenby touched down for the Llanelli side's only try, as Leinster added 21 unanswered points after the break.
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