For a Mac OS X app where a Perl script (Markdown.pl) will be invoked, I need to know if all Mac OS X 10.6 and later installations have Perl installed be default. Otherwise, we’ll have to package it with the app.
Is this confirmed, can I safely assume it?
YES.
And according to the official Snow Leopard specs it comes with Perl, PHP, Ruby, Rails.
This Apple Discussion mentions
Perl (5.8.1)as being pre-installed with OS X 10.6.x.(this last one’s wrong, apparently. See comments of this answer)