How to plot comparsion line and P value in barchart or boxplot?

[whymath]

This is a graph from Graphpad Prism:

How can I plot the comparsion line and P value above bar or box with SAS?

For the convenience of discussion, please use the following code as baseline:

proc sgplot data=sashelp.iris;
  vbox PetalLength/category=Species;
run;

PS: Just ignore the star symbols and use P value instead.

[sasgorilla · Accepted solution]

It looks like this post might have an approach for you to try.