Capturing return value of a function in Pl/Perl

Hi,

I'm calling a plpgsql function in a plperl function.
plpgsql function is a simple select query returning a single row of records.
How can i retrieve the values of different fields in my plperl function?

If i write something like

my $query = "SELECT sp_select";
my $exec = spi_exec_query($sp_select);

How can values returned by executing $query be captured in my perl code ?

Thanks,
Harpreet