perl Pg module and result status

Dear all: i am somewhat new to both perl and PostgreSQL. I am writing
some perl scripts to store and retrieve information in a pgsql database,
using the Pg perl module. However i am having trouble doing checks after
issuing queries or commands.

According to the module documentation:
"
$result_status = $result->resultStatus
Returns the status of the result. For comparing the status you may use
one of the following constants depending upon the command executed:
- PGRES_EMPTY_QUERY
- PGRES_COMMAND_OK
- PGRES_TUPLES_OK
- PGRES_COPY_OUT
- PGRES_COPY_IN
- PGRES_BAD_RESPONSE
- PGRES_NONFATAL_ERROR
- PGRES_FATAL_ERROR
"

When I check the contents of $result_status it is not any of the
mentioned constants, but a number (i am now getting 7 for a
$result->getvalue command after a failed select statement). If i issue
the same select statement in the pgsql terminal everything works. Thus i
don't understand what could be happening.

However, comparisons of the kind of:
if ($result_status != PGRES_COMMAND_OK)
appear to work most of the times (am i comparing against a number?)

Any help is appreciated.

Thanks in advance,

Fernan