How can all these different scripting languages work smoothly with ASP?
The answer is Microsoft's ActiveX Scripting standard. ActiveX Scripting is one of Microsoft's many ActiveX technologies.
ActiveX Scripting says simply this: if you want to develop a scripting language, make sure it supports the standard, and Microsoft will guarantee that it works with Internet Explorer and ASP (among other things).
Microsoft didn't decide to include Perl as a scripting language, someone else used ActiveX Scripting to add Perl capability.

There are some key technologies which will not be supported in Microsoft Edge. A number of these had been deprecated in the past few releases, but moving to a new engine allows us to remove support completely. To ensure future compatibility with Microsoft Edge and other modern browsers, we recommend against any future development or deployment of these legacy technologies. These technologies will continue to be supported in Internet Explorer on Windows 10 for users and enterprises who depend on them.

Web pages with the .asp filename extension use ASP, although some web sites disguise their choice of scripting language for security purposes by using the more common .htm or .html extensions. Pages with the .aspx extension use compiled ASP.NET; however, ASP.NET pages may still include some ASP scripting. The introduction of ASP.NET led to use of the term Classic ASP for the original technology.
ASP runs only on Windows. A number of products emulate some of the functionality of Classic ASP on non-Microsoft web servers. Apache::ASP for example ports Classic ASP to the Apache Web Server, but can only interpret PerlScript.
Sun Java System ASP (formerly ChiliSoft ASP) was a popular and reportedly complete emulator, but it has been discontinued.