On most platforms, since PL/Perl is a shared library, the libperl library must be a shared library also. At the time of this writing, this is almost never the case in prebuilt Perl packages. If this difficulty arises in your situation, a message like this will appear during the build to point out this fact:
*** Cannot build PL/Perl because libperl is not a shared library. *** You might have to rebuild your Perl installation. Refer to *** the documentation for details.
If you see this, you will have to re-build and install Perl manually to be able to build PL/Perl. During the configuration process for Perl, request a shared library.
After having reinstalled Perl, change to the directory src/pl/plperl in the PostgreSQL source tree and issue the commands
gmake clean gmake all gmake install
to complete the build and installation of the PL/Perl shared library.
To install PL/Perl and/or PL/PerlU in a particular database, use the createlang script, for example createlang plperl dbname or createlang plperlu dbname.
Tip: If a language is installed into template1, all subsequently created databases will have the language installed automatically.