always success? - but dont!

Hello,

I have following Code below:
The result is always Success.
I can do:

xxxx . xxx = new    // Success - but it shall not!
yss. ss = new xxx   // Success - ...

yy . sss = new ddd (ff fff)  // Success - but shall not!

left.right = new Form(test.blah)  // only this should be done.
What is wrong

             symbol_def_expr %=
                 (
                 (   symbol_alpha >> *('.' > symbol_alpha)  > '='  >
                 ( ( symbol_new   >
                 (   symbol_alpha >> *('.' > symbol_alpha)  > ('(' >>
                 (   symbol_alpha >> *('.' > symbol_alpha)) >  ')' )))
                 | ( symbol_expr  ))
                 ) )
             ;

TIA
Jens


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