Bala,
I just use the GUI to define the VRL structure.
You could write a Tcl proc to build the VRL definition file from your file (I am assuming the file you have is essentially the definition of the VRL not the data for the VRL) if you are so inclined.
email: jim.kosloskey@jim-kosloskey.com 30+ years Cloverleaf, 60 years IT – old fart.