do {
  print "\nDid I guess your animal?\n\n";
} while ($answer=<STDIN>) !~ /^[YN]/i;

## OR

do {
  print "\nDo you want to <P>lay again or <Q>uit?\n\n";
} while ($answer=<STDIN>) !~ /^[PQ]/i;

##</code><code>##

if ($answer =~ /^P/i) {
  ## Code for P here
}
## Add some elsifs if > 2 choices
else { 
  ## No need to check the final letter
  ## Code for Q here
}