The following features are currently missing from PL/Perl, but they
would make welcome contributions:
PL/Perl functions cannot call each other directly (because they
are anonymous subroutines inside Perl). There's presently no
way for them to share global variables, either.
PL/Perl cannot be used to write trigger functions.
DBD::PgSPI or similar capability
should be integrated into the standard
PostgreSQL distribution.