Add Perl "Hello World" example code

[rmloveland]

Richard Loveland (rmloveland) commented:

We have had a user request for a Perl driver.

AFAICT from some light usage, DBI (with the [DBD::Pg](https://metacpan.org/pod/DBD::Pg] backend] works fine. At least I haven't encountered any problems yet. E.g., prepared statements with placeholders work.

Estimated scope of work:

• [ ) Create new "Hello World" example code in Perl (including retry loop)
• [ ) Write the docs page surrounding it, in the same flavor as the others

Jira Issue: DOC-450