#!/usr/bin/perl -w
use strict; # Every job should
# Start of comments

if (defined undef) {
foo...
}
# End of comments
&do_more_stuff();

##</code><code>##

#!/usr/bin/perl -w
use strict;
use constant COMMENT_WRAPPER => 0;

# Start comments
if (COMMENT_WRAPPER) {
   Blah Blah
}
# End comments
&carry_on_with_stuff();