I didn't tie sigils to the "decline" -- I tied it to the survey's "dislike". I also didn't claim Perl sigils is what drove Python/Ruby adoption. I never claimed a logical cause and effect between sigils and Perl's decline.
Indeed, the Rust language adds a whole new taxonomy of sigils[1] and it's on the upswing in popularity. (Of course, someone will probably come along and think I claimed that "adding sigils to Rust contributed to its growing popularity".)
The decline of Perl's mindshare for new domains was totally separate from "sigils". The usage decline was a 2nd observation of why Perl topped the charts of "most disliked" languages.
>then why did the people who had that problem move to other languages that are even terser
You're asking that question because you're still focused on only one string length definition of "terse".
Let me try another way:
strlen(Rust_code) > strlen(Python_code)
... and yet... Rust can still be perceived as more terse than Python. Why? Because special non-obvious symbols that "don't explain themselves" are perceived as terse. This leads to the paradox that adding to the text length makes it more terse. Lastly, not all opinions about Perl's reputation for terseness comes from Python/Ruby programmers.[1] https://github.com/rust-lang/rust-wiki-backup/blob/master/Si...