in reply to Subclassing DBI and creating two connections
I have the same setup and I suggest to write a wrapper around DBI that provides an handle for reading and one for writing; then use the read handle if you need to perform only reads, or use the write handle if you need to perform both writes and reads. The problem here is the time spent to replicate data from master to slave server: there is no warranty that you will be able to read from the slave the data written to the master few moments before.
For a similar reason don't use now() in any insert or update statement, because the slave will not use the same timestamp used on the master.
In Section Seekers of Perl Wisdom