There is no such thing as too much documentation, no matter how redundant it may be.

Whew! Obviously you haven't seen the code I have.

use warnings; # turn warnings on
use CGI;      # use Stein's CGI.pm for parsing params

my $q = new CGI; # create the CGI.pm instance

# get the customer's name (in the name parameter)
# place in in variable $customer_name
my $customer_name = $q->param("name")

# if the customer's name is "Bobby"
# print "Hi Bobby"
if ($customer_name eq "Bobby") {
    print "Hi Bobby\n";
} else { # if not, print "You're not Bobby"
    print "You're not Bobby\n";
}
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Get the point? This completely distracts from the code and takes way more time on the part of the programmer.

As for subs, I say one comment directly above them. Anymore and the sub is too long and should be broken into multiple subs.