DSL EXPRESSION:
$x =~ "bcd"i


AST:
* statement block
    * bare boolean
        * operator "=~"
            * direct field value "x"
            * case-insensitive regular expression ""bcd"i"

x=abcd,y=ghi
x=ABCD,y=GHI
x=abcde,y=ghi
x=ABCDE,y=GHI
x=ABCDE,y="GHI"
