The symmetric orbifold of \mathbb{T}^4 is the analogue of free SYM in four dimensions, and its dual is described by a tensionless string propagating in {\rm AdS}_3\times {\rm S}^3 \times \mathbb{T}^4. In this paper we study the deformation of this exact AdS/CFT duality away from the free point. On the symmetric orbifold side this amounts to perturbing the theory by the exactly marginal operator from the 2-cycle twisted sector. We identify the corresponding perturbation in the dual worldsheet description, and show that the anomalous conformal dimensions of a number of symmetric orbifold currents are correctly reproduced from this worldsheet perspective.
