What is wrong with:

#!/usr/local/bin/perl -w
#
my $foo;

#=================================#
# This piece of code performs the #
# bar transformation according to #
# the algorithm in Chapter 8 of   #
# Knuth.                          #
#=================================#

sub bar {

    local $something = shift;

    # warning - tricky bit of code here
    # fixed on 9 Aug 2000 by KR to avoid 
    # possible divide by 0 situation

    
    return 1;
}

# and so on
[download]

That is the convention we use here, with most languages. Make the comments stand out, and be generous with them.

Ken