(?-xism:^[^pcd]*(?:(?:p(?!ig)|c(?!at)|d(?!og)))*[^pcd]*$)
dog => 
cat => 
pig => 
owl => 1
conceit =>
contradict =>
captivating => 
purport =>
correct => 

##</code><code>##

$ perl -lne 'print if /^[dpc].*[dpc]/ && !/dog|cat|pig/' /usr/dict/words