Useful functions: a definition of the inverse quote function

It frequently happens that a LISP programmer wants a function to produce a data-structure or function containing constant and variable substructures. The usual solution is to program a form containing a lot of data-structure composing functions (like LIST, CONS and APPEND). The resulting expression is hard to decipher for humans unless more mnemonic constructor-functions are defined. A simple way out is to write the resulting structure with its variable substructures especially marked.