Clipper was really great... I wrote a windowing library in it years ago (DOS type Windows) that I used for contract jobs. I eventually had to move to Clarion though as it was faster to develop in.

I had to work on a VB.NET WinForm program I wrote almost 15 years ago. Someone found an edge case bug in the program that I had to fix. I find that switching languages is not difficult for me. I mostly use C#.NET now, but I used VB.NET (and VB3 and VB4) for many years. Anyway, I fixed the bug and brought the program up to .NET 4.8. It was kind of fun actually. Beats when I had to work in Assembler and Fortran 77. :)