MarkMail provides a very flexible search interface to over 8 million emails from thousands of mailing list archives, and they have just uploaded 530,000 emails from Perl archives dating back to 1999.

The Perl specific home page also shows the trend of email traffic per month since 1999.

From their FAQ:

• MarkMail lets you search millions of emails across thousands of mailing lists
• Search using keywords as well as from:, subject:, extension:, and list: constraints
• The GUI doesn't yet expose it, but you can negate any search item, like -subject:jira.
• Subdomains are list constraining, so tomcat.markmail.org searches tomcat lists
• Use "n" and "p" keyboard shortcuts to navigate the search results
• You're going to want JavaScript enabled
• You can stay current with the MarkMail blog