If I am doing an [fcopy] from chan1 to chan2 I cannot use a
readable fileevent for chan1. This is completely understandable,
but why does it not work the other way round? I would like to copy
data from chan1 but also react to any responses coming from
chan2 as soon as they arrive. However, this is not possible.
Neither is setting a writable fileevent for chan1.

<p align="justify">Though the fix (improvement) was committed into Tcl C-code, the documentation was never updated. The man-page for <tt>fcopy(n)</tt> still states:
<blockquote>You are not allowed to do other I/O operations with inchan or outchan during a background fcopy.</blockquote>
<p align="justify">The above sentence should be clarified and an example of bi-directional fcopy be added.
<p align="justify">BTW, can I multiplex a single source into multiple destinations with fcopy (as <tt>tee(1)</tt> would do)? Should I be able to?