I have several years experience with C++, and this is likely my language of greatest proficiency. I have experience with command-line debugging tools, and some experience with performance optimisation. That being said, I have not yet experienced large-scale software development in C++.
I have some experience with Java, C, Python and Bash. While in no way do I consider myself as experienced at any of these languages, I do have sufficient experience for example to: develop a scanner & parser in Java for an invented language; design and develop the core components of a single processor, asynchronous operating system in C. This has given me some knowledge about the inherent limitations of these languages, and how to design around them.
Additionally, I have worked on projects involving Javascript / Typescript and frontend mark-up. These have involved a mix of legacy and cutting-edge technologies, including Perl and GraphQL.