The first stop along the right direction is Check Return Values and Error Codes. At the surface level, prepare() has failed to produce a statement handle object. But you won't know why until you ask DBI. DBI is very willing to tell you, if you'll only ask it. Consult the DBI documentation for the various ways to do this.

I'm not giving a direct answer based on the belief that Reading the Fine Documentation will benefit you more in the long run.