Expression: 33 @ 127
Infix: Illegal Operator

Expression: 4 % 2 -
Infix: Missing Operand

Expression: 4 2 & -
Infix: Missing Operator

Expression: 3 % { 7 - ( 2 / [ 5 - 81 ] } + 1 )
Infix: Unbalanced

Expression: 2 * 3 + ( 6 / 4 ) - 6
Infix: 2 * 3 + ( 6 / 4 ) - 6 

Expression: 2 * 3 + ( 6 / 4 ) - 7
Postfix: 2 3 * 6 4 / + 7 - 

Expression: 2 * 3 + ( 6 / 4 ) - 8
Value: -1

Expression: 2 * 3 + ( 6 / 4 ) - 9
Prefix: - + * 2 3 / 6 4 9 

Expression: 4 % 2 5 -
Infix: Missing Operator

Expression: ( 43 + + 2 ) * 19 20
Infix: Missing Operand