I start to thing it is a bug. If I use <Key-F2> as event, just an example, it works if no text has been previously selected. Otherwise the following error is prompted :

Tcl::pTk::Error: Can't call method "_retListContext" without a package
+ or object reference at /Users/xxx/perl5/perlbrew/perls/perl-5.24.4/l
+ib/site_perl/5.24.4/Tcl/pTk/Widget.pm line 2842.

    while executing
"if {$catchVal != 0} {
                        if { $retVal != "_TK_BREAK_\n" } { # BREAK ret
+urns are not errors
                                return..."
    (command bound to event)
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