Thanks all for your responses On a closer inspection, it turns out that deep merger indeed works out of the box on v5 without any additional tweaks. (@Henrik - your regex suggestion also works and I can no longer see errors)
We are not looking to stick with v3 forever, just wanted to minimise the number of changes as we make a big leap from puppet 3 to puppet 4 -- You received this message because you are subscribed to the Google Groups "Puppet Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to puppet-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/puppet-users/efde2c1b-303e-4f55-a0e9-5ecc9176e590%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.