All,
In this node, I recommended a solution which had a first step of indexing the position of newlines in a string. I believe my overall approach to be sound, but there are many ways the first step could be accomplished. Since the Anonymous Monk appeared to have speed in mind, I decided to Benchmark a few idea.

I briefly discussed this in the CB before deciding to post it here as there was no obvious concensus reached. Keep in mind there will be an unknown number of newlines but the string itself will be no larger than 200K.

Do you have any other ideas? Use the following string construction for the basis of your benchmark. 
sub build_str {
    my ($str, $max) = ('', 200 * 1024);
    while ( length($str) < $max ) {
        # Assume lines are between 60-79 characters long
        $str .= ('#' x ((rand 20) + 60)) . "\n";
    }
    return $str;
}

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Cheers - L~R

In reply to Finding the positions of a character in a string by Limbic~Region

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