where both `cat` and `grep` can be either shell commands or Red functions and you can redirect input/output from/to variables as well as files. Also you can mixin Red data types, like in example here `%/etc/passwd` is a file instance, not a string.
Also the language itself heavily utilizes this (called Parse dialog) for example they don't have regular expressions at all, JSON is parsed using it as well, GUI system is a fully separate dialog and so on.