Cerny broke the deadlock 11 minutes before the interval, cutting inside and curling a sumptuous effort into the bottom-left corner of Ross Sinclair's goal.
Cerny added Rangers' second, and doubled his account, just before the hour after combining with returning midfielder Ianis Hagi before producing a right-footed finish into the far corner.
Clement's men have now won three matches in a row without conceding in the competition for the first time since doing so across January and February last campaign.
Given St. Johnstone have lost each of their last seven away league games against Rangers without scoring a single goal in the process.
Collection
[
|
...
]