Fifteen years ago, people would have found this interesting.
Yes, Perl is still very relevant today, for me and for countless others[0]
2. Ruby is too 'core' and needs too much additionals gizmos to be efficient
3. Ruby is concise and conventional, while implicitness and terseness are idiomatic of Perl
4. I'm no Perl monk but things in my head translate to code structure more easily in Perl for this use case (unix tools, text/binary/file content stream manipulation)
5. Perl strict mode
6. Occasionally, Perl suid support
7. Bonus: performance under Windows, or rather lack thereof for Ruby
Mind you, Ruby is extremely apt and I enjoy working with it (especially - but not only - with Rails), but this is more a matter of using the right tool for each problem.
There's a load of interesting stuff happening in Perl, I don't use the language myself but I'm interested in what they're up to.