No problem. ;-)

By the way, solution 1 can be simplified further -

#!/usr/local/bin/perl -w
use strict;

my %letter;
while (<DATA>) {
    print, next if /^\s*$/;
    my $c = substr $_, 0, 1;
    print ":$c:\n" if ! $letter{$c}++;
    print;
}

__DATA__
AA ...
A..
[download]

Hey, didn't you like my second and third solutions? ;-)