Try this way,
my @array = $_ =~ m/\b([A-Z]+(?:\d+)?)\b/g;
BROUGHTON VETERINARY GROUP123. Leicestershire mixed practice seeks exp
+erienced vet to replace assistant relocating to Scotland
GIRLING AND BOWDITCH VETERINARY SURGEONS We are looking for an experie
+nced vet for our 5 vet mixed practice.
STANHOPE PARK VETERINARY HOSPITAL. Due to a pregnancy epidemic we are
+looking for 2 new vets, 100% small animal hospital in County Durham.