I have two Perp accounts purchased via two different Steam accounts
I installed two Steam clients to my PC at different folders.
I installed two Perp Clients at each Steam clients
To launch second Steam client it's necessary to close first
I installed additional software SandBoxie http://www.sandboxie.com/
I launched first Steam client normally and second via Sanboxie
So I have two Steam clients working at one PC simultaneously.
And now I can launch both my Perp clients from both Steam clients and it works.