Perl allows programers to create the http headers giving document information. So for example perl could be used to return a binary file, or an image. However for the most part perl scripts return text in the form of html. A perl programer is expected to know html, because their program probably returns it's output to a web browser as an html document. Many companies are hiring people to write scripts in this language.
Many companies choose to keep in house programers too write asp scripts.
Both are roughly equivalent in functionality but have different syntax. Both are enclosed in what would otherwise be html tags. Since asp is a scripting language it is, fairly easy to learn. However scripting languages are scripts because they are simple, and probably restrictive in what they allow the programer to do. Microsoft created a software technology called asp.net which is a compiled version of asp.