Syntactically Significant Capitalization

In ErlangLanguage, capitalization is significant; words beginning with a capital are free variables and those beginning with a lowercase are barewords or function names.

my_fun( [ list_tag | ListOfThings ] ) -> do_stuff(ListOfThings).

means that my_fun is a function that, when called with a list whose car is the bareword "list_tag", does some stuff with the cdr of the list.

Are there other languages with syntactically significant capitalization?

Although CeePlusPlus and JavaLanguage technically do not have syntactically significant capitalization, in practice they do. This is because of the CppIdiom? and JavaIdiom to capitalize ClassNames and use lower case for instancesOfClasses.

See also SyntacticallySignificantWhitespace, CapitalizationRules.