So...

if ($ENV{REMOTE_ADDR} eq '180.76.6.175') {

works as

if ($ENV{REMOTE_ADDR} =~  /^180\.0?76\.0{0,2}6\.\d{1,3}$/) {

what would a wild card for :

if ($ENV{REMOTE_ADDR} eq '180.76.6.') {

and 

if ($ENV{REMOTE_ADDR} eq '180.76.') {

look like ?