in reply to Insert comma after every character
my $str = "ABCDE"; print join(",",split(//,$str));
The code above enters a comma after every character, except the last one (as shown in your example). However it does not distinguish if your character is between [A..Za..z].
If you want to stick to your solution (using a regex), replace \d by \w. (\d is for numbers.) However your solution adds a comma after the last character.