insert taxonomy through computed field or php code?

I'd like to have the authors name automatically created as a term for bio. NAT won't work as the created term doesn't link to the bio. I tried experimenting with computed field just to create a term using this code

This nearly worked. The term appears in the term_data table in mysql but not as a term in Drupal's vocabulary.

Afterwards when I try to add a term from the add terms form in Drupal, I get in error and then term which I tried unsuccesssfullly to insert using computed field then magically appears!

Any idea of code I can use to add a term to a vocabulary from computed field?

Once I get this accomplished I should be able to substitute the authors name using a variation of this code: