$ perl -Mstrict -Mwarnings -e '
    use Scalar::Util qw{dualvar};

    my @string_array = (
        "Hello, my name is John",
        "How are you?",
        "blah (blah)",
    );

    my @count_array;
    my $last_count = 0;

    for (@string_array) {
        push @count_array => dualvar $last_count, $_;
        $last_count += length;
    }

    printf "%08d %s\n" => $_, $_ for @count_array;
'
00000000 Hello, my name is John
00000022 How are you?
00000034 blah (blah)