Effect of clocking block on uvm driver/monitor

In reply to chr_sue:

Thanks for the reply i would like to know what are the issues will arise if we use #0 input skew in clocking block.
Even though signals are sampled in observed region(#0) and stimulus is driving in the reactive region (output #0).
I am bit confused with the sentance:
" input#0 sampling allows our testbench a “sneak preview” of the value of a signal after the effects of the current clock. Normally your testbench would not be able to see that new value until the next clock."
please provide me an example it would be helpful.
Thanks in advance