Yes, they are both mature, but Perl is also evolving, especially with the active development of Perl 6 (actually even Perl 5). Being mature and evolving are not mutually exclusive, in this sense, Perl shares a path that is more similar to Java's.
To be fair C++ isn't standing still either. See Strousop's The design of C++0x (pdf) for example.
It's just a bit harder to spot since perl doesn't have the advantages of multiple implementations and a standards body ;-)