plperl and plperlu language extentsions

Hi,

I am running postgres 10.4 on CentOS 7.5. I am having trouble getting the
plperl language extension going :

netdrms02.nispdc.nso.edu:5432 postgres(at)nsocu=# CREATE EXTENSION plperl;
ERROR: 58P01: could not open extension control file
"/usr/pgsql-10/share/extension/plperl.control": No such file or directory
LOCATION: parse_extension_control_file, extension.c:494

Sure enough that file is not there :

[production(at)netdrms02 ~]$ ls /usr/pgsql-10/share/extension/
plpgsql--1.0.sql plpgsql.control plpgsql--unpackaged--1.0.sql

Yet plperl would seem to be installed :

# yum list | grep postgres | grep perl
postgresql-plperl.x86_64 9.2.23-3.el7_4
base
postgresql10-plperl.x86_64 10.4-1PGDG.rhel7
pgdg10

I need to do this for both plperl and plperlu. I think there is perhaps
something I don't have installed, but I can't tell what? I apologize if
this is obvious, the language extensions are not something I deal with
regularly.

If it helps, here is the result of "select version();" :
PostgreSQL 10.4 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-28), 64-bit

Thanks for considering this,

Niles.

--
Niles Oien, National Solar Observatory, Boulder Colorado USA