One feature I like in Perl 5.10 is relocatable @INC support. From the commit by Nicholas "You can install things to the current location of the perl tree, move it, install more things, move it again, lather rinse repeat".
mkdir tmp && cd tmp wget http://www.cpan.org/src/perl-5.10.0.tar.gz tar fzx perl-5.10.0.tar.gz cd perl-5.10.0 sh Configure -de -Dprefix=/home/acme/perl_5_10_0 -Duserelocatableinc make && make test && make install /home/acme/perl_5_10_0/bin/perl -e 'use feature qw(say); say "hi"' mv /home/acme/perl_5_10_0 /home/acme/newpath_perl_5_10_0 /home/acme/newpath_perl_5_10_0/bin/perl -e 'use feature qw(say); say "hi"' # etc.
