Larry Wall said once that he added sigils in Perl so he could freely add features to the language without conflicting with other's peoples variable names. It's a language design choice that makes sense for Perl's maximalism approach to features.

Perl is very well thought out, in a way that I don't think gets enough credit. For example, the three loop controls (next, last, redo) are four letters long, which makes remembering them easier. In a world where I sometimes have to jump between languages I haven't used in a while, and I'm always forgetting what arbitrary word choice this particular language used for a feature, it's nice to come back to Perl and have a language where the grammar is a little bit less arbitrary.