You might not have Apache::Session installed. When I run your sample code I get:

Can't connect(   HASH(0x8202dd4)), no database driver specified and
DBI_DSN env var not set at
/usr/local/lib/perl5/site_perl/5.6.1/Apache/Session/Lock/MySQL.pm
line 36
[download]

Check to see if you have the module installed by running from the command line:

perl -MApache::Session -e "print Apache::Session->VERSION"
[download]

On my machine, I get '1.54' displayed.

Chris
M-x auto-bs-mode