• Get it working first, optimize (or refactor if you want to sound hep :) afterwards.
• Keep in mind that if you're interpolating variables you've implicitly used the . operator
• Heredocs (<<EOT) are much more readable (IMHO) than fifteen gazillion .= lines (I mean come on, this is perl not C or Java)

Update:As was pointed out to me in a msg, strictly speaking refactoring isn't optimization; however refactoring may improve performance by replacing an inefficient implementation with a better designed one. Pardon me for attempting humor. :)