WARNING in parallel index creation.

If i run:

pgbench -i -s30

And then create the function:

CREATE OR REPLACE FUNCTION foobar(text)
RETURNS text
LANGUAGE plperl
IMMUTABLE PARALLEL SAFE STRICT COST 10000
AS $function$
return scalar reverse($_[0]);
$function$;

Then when I create in index, I get a warning:

jjanes=# create index on pgbench_accounts (foobar(filler));
WARNING: cannot set parameters during a parallel operation
WARNING: cannot set parameters during a parallel operation

If I create the index again within the same session, there is no WARNING.

This only occurs if plperl.on_init is set in the postgresql.conf file. It
doesn't seem to matter what it is set to,
even the empty string triggers the warning.

plperl.on_init=''

As far as I can tell the index is created correctly despite the warning.

Cheers,

Jeff