The solution works well without any error.
Dear Andre, Ansley,Thank you so much for the timely help.
The code I used is:
set region/x=66.4E:100.1E/y=6.4N:38.6N/t=01-JAN 12:00 to 31-DEC 17:48
! Repeat on 10.5deg Latitude
repeat/x=76.25:79.75:.25 (go test.jnl)
let rf = rf_clim[y=10.5N, l=1:365 ]
===============================But there is a problem in creation of the graph files.
It seems that x assumes only integers in creating file name. The files created are:
Value of x ranges from 76.25 to 79.75 in steps of .25. The gif images are created, but files names are not created for decimal values.