> install_driver(mysql) failed: Can't locate DBD/mysql.pm in @INC

That means that either DBD::mysql is not properly installed (in which case, re-install it), or else the location it is installed in is not in your @INC (in which case use "use lib" to add the directory where it is located to the @INC).

> I tried adding an extra : in the code between dbi::mysql

Since DBI treats whatever is between the first two colons as the driver, you are essentially telling DBI to operate using the driver named ''. Hence the message "no database driver specified".