[cobythedog]

The current version (11) does: https://www.postgresql.org/docs/11/sql-createprocedure.html

[paulryanrogers]

That is the command to create one, but the syntax of the definition body is what does not comply with SQL/PSM.

Looks like there is an extension but it hasn't been updated in 8 years as doesn't appear to be production ready yet[0]

[0] https://github.com/okbob/plpsm0