What a joy! This solves our problem at the root(not the topic of the thread) in a much better way than I hoped. To call a Perl subroutine from within the Tcl code is very simple (the Tcl is really great indeed!):

use Tcl::Tk;

my $mw = MainWindow;
my $int = $mw->interp;
$int->CreateCommand("MySubroutine", \&MySubroutine);
$int->Eval();

sub MySubroutine{
...
}

Mainloop;
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