We had an similar issue long ago when starting Java.

• in my experiences, the best is doing code-reviews, with constantly changing teams of 5-6 developers - that way the author and the reviewer learn something
• you can also let the developers create a code-review-checklist and a perl coding guideline/best-practices - this forces them to look even deeper at the language
and to reflect on the way they code
• as others said, involving an (external) expert to support that is helpful

HTH, Rata