I'm curious about which (if any) real-world programming languages have a regular grammar (i.e. the set of all syntactically correct programs is regular).
See also this question: What programming languages are context-free?.
Brainfuck and Whitespace and similars are certainly regular.
On the other side, any language that supports (parens) is not regular, as the automaton recognizing it would need a stack. And I don't really know many languages without (){}[] support that would do anything more than assembly.
Only real-worldy example that comes to mind and probably is regular is Forth.