We investigate how dense, compact shells of circumstellar gas ejected by a red supergiant presupernova star late in its life before collapse and explosion can affect the optical light curves of the resulting type IIP/IIL supernova, taking the particular example of SN 2013ej. We find that the post-explosion light curves resulting from such stars and their CSM reproduce the light curves upto the beginning of the radioactive tail phase substantially better than those without that enhanced mass loss and hence having no dense, nearby CSM. The explosion energy for the progenitors with a dense CSM is reduced by almost a factor of two compared to those without the CSM. These explosions may represent an intermediate class of supernovae between type II-P/II-L and type II-n SNe with the characteristics of simultaneous UV and optical peak, slow decline after peak and a longer plateau. We also present the velocity profiles of the star as well as photospheric velocities at various times post explosion and study the effects of varying amounts of radioactive nickel on the light curves.