AND
    	^		bitwise XOR
    	|		bitwise OR
    	&&		logical AND
    	||		logical OR
    	expr ? expr : expr
    			conditional operator
    	=, *=, /=, %=,
    	+=, -=, <<=, >>=,
    	&=, ^=, |=	assignment
    
    Shell variables are allowed as operands.  The name of the variable
    is replaced by its value (coerced to a fixed-width integer) within
    an expression.  The variable need not have its integer attribute
    turned on to be used in an expression.
    
    Operators are evaluated in order of precedence.  Sub-expressions in
    parentheses are evaluated first and may override the precedence
    rules above.
    
    Exit Status:
    If the last ARG evaluates to 0, let returns 1; let returns 0 otherwise.