+1  A: 

In Riena specifically, the tabs that you see are 'sub-applications' and not perspectives. Riena has a slightly different approach to the UI and the Look and Feel than traditional RCP / Eclipse applications do.

Take a look at the Look and Feel section on the Eclipse wiki to get an idea. Also, you could download the source-code and get started with Riena quite quickly and see for yourself how they do it.

Anirudh
A: 

Check for the plugin preference:

*org.eclipse.ui./DOCK_PERSPECTIVE_BAR=left*

Read the below for exact details:

How to change perspective bar pos

I am not sure whether the above link will take you to the exact index. If not Click on the link and check Question 12: How can I change the default UI settings for the perspective bar location, fast view bar location, etc?

Suraj Chandran