You wrote:

"... I am selecting 15 values, I am not sure where its getting 12 from"

After I wrote:

"... I assumed that was selecting the 15 columns ... I then removed the 3 elements ... for which placeholders did not exist ..."

15 - 3 = 12
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But you don't even need that simple arithmetic: simply count the placeholders in the VALUES clause of your INSERT statement.

I suspect you're missing something very fundamental: maybe a lack of knowledge or understanding. Perhaps revisit DBI; in particular, the "Placeholders and Bind Values" section.