Er, no, open(my $fh, "...") is correct usage. $fh is autovivified into an actual filehandle (not just a symbolic reference). It is the preferred method for opening a filehandle without clobbering an existing one. The excerpt you are referring to does mean an undefined scalar variable ($fh), not a bareword (FH).

perldoc perlopentut provides several examples of this in the Indirect Filehandles section.