Perl is installed by default on most Unix systems. FreeBSD being the exception. Python isn’t. Although Python is popular; if we’re comparing the probability of someone having the interpreter installed already, it’s greater for Perl, even if people aren’t aware they already have it.
Though one would probably never be able to work with an assumed install of Python anyway because one would not be able to assume a specific version. I am guessing this is a lesser problem for Perl, since it’s been frozen at some version of 5 for the past 25-30 years correct?