Sorting lines is easy: everybody knows the sort command.
But what if you want to do the other way around?
The above perl one-liner does just that:
-MList::Util load the List::Util module (as if doing use List::Util inside a Perl script)
-e '...' execute Perl command
print List::Util::shuffle <> call List::Util::shuffle for the lines coming from standard input, read by <>
Another way would be sort -R if your version supports that (GNU, as opposed to BSD). In BSD systems you can install coreutils and try gsort -R instead. (For eample on OSX, using MacPorts: sudo port install coreutils.)