No, this page is not for flame wars or anything. I use Tcl as well as Perl and Python.
Which language I choose for which task is decided by my feeling.
Sometimes I just feel like coding Perl, sometimes I feel like coding Tcl. There are no big differences to my knowledge that would make one language THE choice for a certain type of tasks, or am I wrong? - Moritz
It's my opinion that, in general, you are correct. However, some tasks may be more easily done in one language than another.
For instance, Perl and Python comes with different extensions and functions than Tcl. So to do equivalent things in Tcl, you either have to locate, download, and install an extension which you seek out to do the functionality, or you have to learn enough about the topic to write your own extension.