Top N Most Common Mistakes

[Smith, Donald T.]

> You still get the people who imagine that because variables are
flagged 
> with a "$" sign they must work by textual substitution.

I don't have the CS background to quite understand how variables work
via textual substitution and how they work some other way. I do know --
from reading Michael Kay's books -- that XSLT is a functional language
and that variables in XSLT can't be updated. I do understand quite well
template-based processing and recursive templates.

If it's not too much of a digression into CS theory, could someone
explain this point?

Thanks,

Don