It seems that function get arrays as strings in plperl.
This is a little workaround who want pass arrays to plperl functions
my( $strarr )= @_;
$strarr =~ s/{/[/g;
$strarr =~ s/}/]/g;
my $arr= eval $strarr;
NOTICE:
you must create you function as plperlu
and add language:
create language plperlu;