I have included below lines as well. I think I don't need below lines at all. I hv commented out them now

Yes, all the loop does is print. Since you have commented out the print line the loop becomes a no-op and may as well be removed entirely.

my ultimate goal is to have a STACK bar chart since I have another file /tmp/recipients.txt.

I'm not sure why you would want to stack unrelated senders and recipients. Regardless, I'll let someone who actually uses GD::Graph guide you on that one. Good luck.