[perigrin]

Odd number releases are dev releases, even number are production releases. After 5.12 or so releases became time-boxed so that there is a new even release every year around this time (hence 5.28.0-rc1 dropping now, and in a year 5.30.0 will drop).

[gkya]

I guess you mean "9" in 5.9.2 as the part that tells dev or production, no?

[perigrin]

Yes. Because of a naming … inconsistency … several core developers and major CPAN contributes have moved the 5 into the name of the language. So Perl5 version 9.2 or Perl5 version 28.0-rc1. Because we are often quirky nostalgic humans we usually leave the 5 where it traditionally has been at the start of the version string.