Historical version. PostgreSQL 8.0 has reached end of support. See the current manual.
37.7. Limitations and Missing Features
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).
SPI is not yet fully implemented.
In the current implementation, if you are fetching or returning very large data sets, you should be aware that these will all go into memory.
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Read the upstream documentation. For corrections, first check the current manual.