What I'm trying to achieve is to keep the dbi/sql object instantiated in the constructor by adding it to the hash that is the object (i.e. as a property) The subroutines can then grab that from the hash and use it, rather than having to re-create it.

Is this app single threaded? If not, be sure to read up on DBI - Threads and Thread Safety.

Also, how are you dealing with disconnected database handles? Have you seen DBIx::Connector?