If your goal is to learn programming languages, I would recommend you to do it on a PC. The debuggers (and the amount of free language implementations) are way better there.

If your goal isn't to learn programming languages, but to do "fun things" with microcontrollers, I would recommend that you take another look at C.

There is this saying "a minute to learn, a lifetime to master". The thing is that you can learn enough to start wriging C programs very quickly. The only bad thing with C is that it has few limitations. So when do do wrong, there is no padding to protect you. The compiler will accept your code, and when you say "jump", the microcontroller will jump even if there is no where to land.

But that isn't really a big problem. If coding incrementally, adding a few lines at a time, you will see that good code gives good results. And there are lots of forums (including this one) where you can get help if you get stuck.

You think you want to test a little bit of everyting. But let's switch to something else. Would you try to be a carpenter and try getting something done with a pen knife, if you also have better tools available? If you try use C, you will find thousands and thousands of code fragments you can read and learn from. And you will find thousands of developers who can help you if stuck.

Nothing wrong with using Pascal - if that is a program language you know well and loves. But it isn't a preferred language to use if you want mainstream help from others. And Forth is an interesting language that was much used once, when microcontrollers didn't had any available compilers - or when the compilers were much too expensive for any hobbyist. But you are living in a different time, and with your access to Internet your options are completely different.

Use BASIC if you like. But if you want to try someting else, do select C. And if you want to learn more - try your hands at assembler. Just remember that the need to be able to code in assembler have greatly diminished with time because of constant improvements to microprocessors. Lots of developers do manage well with just being able to read and understand assembler (which means that they can look at the translation from C to assembler and understand what the compiler actually did). And before someone quickly jumps in with arguments that assembly knowledge is vital - remember that there is a huge difference between a hobbyist and someone working full time as developer. Professional developers shouldn't push their metrics onto hobbyists.