From MorphOS Library
UnSetEnv - Removes a global variable
NAME - Name of the variable to remove SAVE - Permanently remove the variable (see Below)
UnSetEnv removes the named global variable from the current variable list. Please note that if the variable has been Set using the SAVE switch, it will be available again after a Reboot. To remove it totally, use the SAVE switch.
NOTE: With no arguments, UNSETENV lists the current variables.
See also: SetEnv, Set and UnSet.