Windows only.
Certain COM objects, for example, VT_BLOBs, cannot be represented in APL or may be in error. By default Dyalog will generate a DOMAIN ERROR in these cases. For COM objects of type VT_EMPTY the interpreter by default returns ⎕NULL.
2041⌶ allows the APL programmer to specify what is returned by the interpreter in these cases.
Y may be 1 or 2.
If Y is 1, then X specifies the value that is returned instead of ⎕NULL when the COM object is of type VT_EMPTY.
If Y is 2, then X specifies the value that is returned when the COM object is in error, or is of a type that cannot be represented in APL.
In both cases, omitting X results in the default behaviour being restored.
R is the previous value specified; if there was no previous value then this function will perform its task but generate a VALUE ERROR.