_______TCL EG. WORKS WELL______
pack [entry .e1 -textvar v1 -width 50]
set v1 blob
pack [entry .e2 -textvar v2 -width 50]
set v2 blob
proc cb_entry {my_str} { puts -nonewline $my_str; flush stdout}
bind .e1 <KeyPress> {cb_entry $v1; break} ;#<======= break here
bind .e2 <KeyPress> {cb_entry $v2} ;

_______PERL EG. NEEDS BREAK_______
use Tkx;
my $mw;
sub cb_entry {my $win=$_[0]; $mw->g_wm_title("this is $win m8");}

sub main_loop {
my $v1;
my $v2;
$mw = Tkx::widget->new(".");

#WHERE AND HOW TO SPECIFY BREAK IN HERE????        
my $e1 = $mw->new_ttk__entry( -width => 50, 
-textvariable => \$v1, );
$e1->g_pack( -expand => 1, -fill => 'both', );
Tkx::bind($e1, "<Key>", [
    sub { cb_entry($_[0]);   }, Tkx::Ev("%W")
]); 

my $e2 = $mw->new_ttk__entry( -width => 50, 
-textvariable => \$v2, );
$e2->g_pack( -expand => 1, -fill => 'both', );
Tkx::bind($e2, "<Key>", [
    sub { cb_entry($_[0]);  }, Tkx::Ev("%W")
]);
     
    Tkx::MainLoop(); 
}

main_loop;