Which falls prey to the fact that people don't need to disambiguate "perl" when searching, but often do for "python". Changing it to "perl" and "python language" isn't very useful either, as it so severely limits the python query as to be unusable.
To be clear, I don't doubt there is a drop in Perl mindshare and usage, I just don't think the original comparison, or the alternative one you posted, really shows a relation between Perl and Python in any meaningful way.
No, it doesn't. There's no reason for the proportion of people looking for perl related stuff who use "perl language" as a search term to change over time. That proportion might affect the absolute numbers, but not the trends.
To be clear, I don't doubt there is a drop in Perl mindshare and usage, I just don't think the original comparison, or the alternative one you posted, really shows a relation between Perl and Python in any meaningful way.