1.4.2 External Rexx programs Regina searches for Rexx programs, using a combination of the REGINA_MACROS environment variable and the addition of filename extensions. This rule applies to both external function calls and the program specified on the command line. Assume you have a call to an external function, and it is coded as follows: Call myextfunc arg1, arg2 First, Regina looks for a file called myextfunc in the current directory. If it can't find that file, it looks in each directory specified in the REGINA_MACROS environment variable for a file called myextfunc. If the file is not found, Regina then attempts to find a file called myextfunc.rexx in the current directory, then in each directory in REGINA_MACROS. Regina continues, next by appending .rex to the supplied external function name, and lastly by appending .cmd. Only if a file does not exist in either the current directory, or any directory in REGINA_MACROS, either with the supplied filename or with that filename appended with .rexx, .rex or .cmd does Regina complain that the external function is unknown.