An esoteric programming language where everything is functions and strings, where the only built in operation is to interleave two strings.
Note
I need to work this out more.
The only allowed symbols non-negative integers and the symbols ., , >, <, #, ! and :. Comments follow after any - sign and any text there is ignored. Leading zeroes don't change the meaning of a symbol: 1 and 01 are considered identical.
All values are strings. The following things are built in ways to obtain strings.