COBOL was written in the 60s and has been in mission critical stuff for decades. Neither of those factors means it's the right tool for the job now.
The things I'm recommending that are more mature are Go, Python, D, Rust, or any other language that is more verbose and maintainable than regular expressions. Anything with a full debugger, IDE support, and useful error messages is a better choice.
Except COBOL often is the right answer for text processing now, meets all your criteria (debugger, IDE, maintainable, etc) and far more mature than Go, Python, Rust or D (really...D?).
Which could be said about any newly fashionable language. Or any niche language. And in the case of COBOL, it's not even true. Here's a little hint: just because you don't know any COBOL programmers, doesn't mean they don't exist. My own company has a couple of hundred, and we have an outsourcing partner that has a several thousand. We are not unique.
The things I'm recommending that are more mature are Go, Python, D, Rust, or any other language that is more verbose and maintainable than regular expressions. Anything with a full debugger, IDE support, and useful error messages is a better choice.