DSL EXPRESSION:
$x =~ "bcd"


AST:
"block" [tt:block] [nt:StatementBlock]
    "=~" [tt:op_eqtilde] [nt:BareBoolean]
        "=~" [tt:op_eqtilde] [nt:Operator]
            "$x" [tt:field_name] [nt:DirectFieldValue]
            ""bcd"" [tt:string_literal] [nt:string_literal]

x=abcd,y=ghi
x=abcde,y=ghi
