I don't think that is the case. Sure Perl may have been in decline for ages, but people were not comparing Perl to Python for that long. Simply because python hasn't existed that long.

Python 2.0 was released in 2000. Python 1.0 was 1994, and Python 0.9 (first public release?) was 1991.

Check the google trends. https://trends.google.com/trends/explore?date=all&geo=US&q=p... Its unclear when perl peaked since it has been in decline since before 2004 But it wasn't til late 2007 that Python overtook Perl in google searches

Even while it was in decline people were still making that argument.