open a terminal and type:

perl -le 'print for @INC'

you should see all directorys in @INC. Now try this with the apache user, there for type:

su -
su - YOUR_APACHE_USER_NAME -c "perl -le 'print for @INC'"
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there should be some slide differences bettween them and this should be the reason for your problem.

Try this in a new terminal:

perl -MData::Dumper -MDBD::mysqlPP -le " print Dumper( \%INC ) " | grep "DBD/mysqlPP"

now you can add the shown directory in your script like this:

...
use lib qw( DIRECTORY_PATH );
use DBI;
use CGI qw(:standard);
...
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sure not the best way to do this, but it should be work out.