Raymond,

&& is always used to signal an end of line comment, the parser doesn't acknowledge that they are appearing inside a string constant. So your code fails because it ends up being an incomplere command ? strtran("change

This will work though:

? strtran("change &" + "& to something", "&", "a")

>? strtran("change && to something", "&", "a")
>
>fails with "command contains unrecognized phrase/keyword".