Help,can i generate a random number using irule?

I want to generate a random number first,and then add this number to the end of http uri.

 

 

I have found a funtion in TCL Reference:

 

 

srand(arg)

 

The arg, which must be an integer, is used to reset the seed for the random number generator.

 

Returns the first random number from that seed. Each interpreter has it’s own seed.

 

 

But,how to use it?