I figured it out!! its the data.
just multiply the data by some decimal number say 
foreach $i (@data){
$i = $i *1000; }
get the distinct values and proceed to the histogram. The bins seem to work for only integers.(I am still a novice , please correct me if i am wrong).
So if anyone has decimal numbers and need to plot histogram. just scale it!!!

Thanks a lot for the all help! This site is very helpful. I am learning a lot