my $Line = "1243 That will efficiently match a nonempty group with matching parentheses two levels deep or less.";

if ($Line =~ /^(?!.*\bgroup\b)(\d{4}) ([^.]+?[.\!\?])$/){
	print "$1\n$2\n"; #Does not print
}
elsif ($Line =~ /^(?!.*\bgXroup\b)(\d{4}) ([^.]+?[.\!\?])$/){
	print "$1\n$2\n"; #Prints
}