package SybaseInterfaces;
....
my %lookup_iptoname = ();

sub syb_gethostbyaddr
{
    my $self = shift;
    my $class = ref($self);

    my ($my_ipaddr) = @_;

    #  We cache the name lookups to increase performance and reduce network i/o
    unless (defined $SybaseInterfaces::lookup_iptoname{$my_ipaddr})
    {
        $SybaseInterfaces::lookup_iptoname{$my_ipaddr} = gethostbyaddr(inet_aton($my_ipaddr), AF_INET);
    }

    return ( $SybaseInterfaces::lookup_iptoname{$my_ipaddr} );
}