The statistics are interesting, but what do they say? Is there any reason to believe that these figures say anything at all about "popularity" of a programming language and/or about the trend you seem to have found?

And do you have to follow a trend? See what the "trend" was in Germany in the 1930's and where it lead to.

Finally, your figures shouw a tripling of "Perl"-references over the time period investigated. not much of a "demise", I'd say.