I'm not aware of any "modern" language having that feature, at least outside of the languages without much syntax (Scheme, Lisp derivatives), where it is easy to introduce new forms or which have (real) macros as a built-in language feature.
In reply to Re^3: Perl 6 grammar question
by Corion
in thread Perl 6 grammar question
by Anonymous Monk
| For: | Use: | ||
| & | & | ||
| < | < | ||
| > | > | ||
| [ | [ | ||
| ] | ] |