Conc. perchloric is bloody scary stuff, at least when its past 60-75%, then it has to be handled with the greatest respect.
Not only a very strong mineral acid, and oxidizer. Also, if it contacts organic materials such as labcoats, wooden bench tops, etc. it can form shock, and friction-sensitive explosive materials, that can come out to bite the chemist later. Also, its a bugger for fume hoods, as it can build up explosive organic perchlorate derivatives inside the ductwork that goes off later.
I have a big bloody burn scar on one hand, from picking up some glassware that had conc. HClO4 wetting the outside. That was years ago but the scar covers about 2/3 to 3/4th of my hand still.