For me, "modern Perl" refers to 5.8, with its use of utf8 internally for all character-based operations, its Encode module for inter-operating with virtually all non-Unicode character sets, and the PerlIO layers. The first two points make Perl a serious player (in fact, a tremendous asset) for dealing with human languages other than English, and PerlIO brings amazing simplicity to the scripting of some really powerful concepts.
When I write scripts using these resources, it's hard (or scary) to imagine how I would get my work done without them.