R- package for Parametric Survival Analysis with Left-censored data

Dear All,

I am new to R. Can someone please direct me to an R package using which I can estimate a Parametric Survival Analysis model with Left-censored (delayed entry) data in it. 

I recently received reviewers comment on my submitted article, where the reviewer suggested that only R has capabilities of estimating above mentioned survival model. However, I am not able to figure which specific package in R, the reviewer was referring to. 

Any pointer would be greatly appreciated !!

cheers,

Vinod Mishra