# You had
for ($l_count = 1; $l_count < $l_len; $l_count++)
{
$lower=$lower."9";
}

# Try this instead:
for my $l_count ( 1..$l_len ) {
    $lower=$lower."9";

}

# To build up a string like this you should be using the 'x' operator
my $lower = '9' x $l_len;