you can but.. why would u want to? Royal plecos need vegetables, fruits and wood.. not blood worms.. they might not even know that its food and probably might not eat it.
panaques dont have the ability to digest meat protein the same as other plecs do, it is believed that too much protein can cause bloat and other digestive problems, especially with Royals.
I have a royal with my 3 fire eels.. had them together for awhile now. The only concern I have is the royal latching onto an eel to chill and do damage. Never had an issue with it going after the eels food. I do give my pleco lots of drift wood options, zucchini, sinking wafers, and other assorted veggies though so he's not "starved" to try the worms. I've never seen him even go near the eels while feeding.
I currently have a small Royal...it's best to feed a variety, but I feed my tank bloodworms and it goes after it as well. It usually just munches on the driftwood in the tank when there isn't any food to go after.