It is possible to specify that a procedure name is global, constant, a procedure identifier, a lexical constant a lexical variable, or temporarily redefined local to a procedure, using forms like
define global <name> ...
define global constant procedure <name> ...
define global vars procedure <name> ...
define lconstant procedure <name> ...
define dlocal procedure <name> ...
etc.
In short, the kinds of specifiers that can occur in a variable declaration can also occur in a procedure header.
See HELP VARS, HELP LEXICAL, REF IDENT, REF SYNTAX