Perl was invented because the gap from shell to more capable languages was (and is) really big. Languages like Python and Ruby didn’t exist yet, and Perl had a really, really strong sweet spot in text processing.
Still does.
Ubiquity, speed, and conciseness.
Perl is usually installed by default on Linux and Unix systems. Ruby might be there, it depends.
Perl is faster than Ruby. Ruby has been one of the slower scripting languages. But Ruby has been working on performance improvements in the past few releases. I have not seen any benchmarks of the current Perl versus the current Ruby, so this may have changed.
Perl is more concise than Ruby allowing more functionality for less code.
The JVM would like a word. (It has slow startup, but can be very fast at runtime due to JIT optimization and cacheing.)
Scripts should start and run quickly.
Ruby has historically been fairly slow which is why Ruby 3 focused heavily on performance. It has been improving a lot, but I have not seen any benchmarks against other programming languages.