As usual, you can get it at http://search.cpan.org/dist/perl/ and build it from
source, and presumably the various OS-specific binaries will be available soon.
And for the small number of you on Windows, http://strawberryperl.com/ would
be the best source for you, once they've updated any day now.
See http://search.cpan.org/dist/perl/pod/perl5101delta.pod to know what changed
in 5.10.1 from the 5.10.0 release last 2007 December.
Changes include some improvements to the behavior of 5.10.0-added features like
smart-matching and switch statements, and 5.10.1 has some other feature
additions such as the Unicode Character Database 5.1.0 and DTrace support, and
bug fixes are made including some regressions that 5.10.0 had over 5.8.8; so if
you avoided upgrading to 5.10.x from 5.8.x due to a regression, that should no
longer be a concern now.
This is now the main version that I am using.
-- Darren Duncan