Control File: invalid variable name, '}' is missing

Control files can include shell like variable references defined starting with a dollar sign and a name written between curly brackets as in: ${VERSION}. The variable name cannot include any curly braces, however, the closing curly bracket must be present. This error is generated when the closing bracket is missing.

Architecture: ${ARCH_OS}-${ARCH_CPU}
Architecture: ${ARCH_OS-${ARCH_CPU}