Thanks for your interest and notes re: broken links. I'm glad to hear my little toot has helped. I've fixed things as noted below:

• Hashes, as explained in PerlGuts Illustrated, by Gisle Aas (Has been replaced with a link using the Wayback Machine)
• Perl.com: How Hashes Really Work, by Abhijit Menon-Sen (Works for me...)
• Effective Perl: Intermediate and Advanced Topics contains a wealth of information, not limited to hashes, but also including several pages on Joseph N. Hall's PErl Graphical Structures (PEGS). (Has been replaced with a link using the Wayback Machine)