Exactly. Like this, for example:

use feature 'say';

my $output = "data.txt";
open(DAT, '+<', $output) || die("Cannot Open File");
my $id;
while (<DAT>) {
    ($id) = m/\A(\d+):/;
}

say DAT join ':', ++$id, $name, $number, $address, $phone, $email;

close(DAT);
[download]

Better yet:

use feature 'say';

my $output = "data.txt";
open(DAT, '+<', $output) || die("Cannot Open File");

my $line;
$line = <DAT> until eof DAT;
my ($id) = $line =~ m/\A(\d+):/;

say DAT join ':', ++$id, $name, $number, $address, $phone, $email;

close(DAT);
[download]

This way, the regular expression is only executed once - on the last line.

Sorry for the double post, I can't edit my comments (not enough powers yet).

Thanks for the quick response and multiple answers...each worked and now I know that I have to read the line before instead of just adding. This makes things easier as before I was using a pattern match in order to edit my entries in the database and now all I have to do is enter a line ID number and I am good to go. Thanks again!