I would post this as a bug report, but I know that wouldn't fly. It just really feels like a bug or unfortunate limitation.
In this day and age of JSON API, which is very often a single very long string without any sort of line breaks, often much longer than 8000 bytes... there is just no practical use for features like $urlget() without the means to read and parse a file or &binary variable with lines that exceed 8000 bytes of text.
Please add &binvar input support to $regex(), $regsub() and $regsubex()
The capability of PCRE to handle strings longer than 8000 bytes is without question. We just currently have no way to send long strings to PCRE to be pulled apart by regex.
We simply can't find very much, if any, use for functions like $urlget() unless we can pass their &binvar contents to be chopped up by regex into useful digestible pieces using simple regex templates for parsing JSON (and XML, and etc).
I promise I won't ask again.