for(0..9){
        $input=$_;
        $_ = $left_num -> Button(
	     -text => "$input",
	     -background => 'grey',
	     -width => 5,
	     -height => 2,
	     -command => $number=$number==0||$equals!=0?$input:$number.$input,
    ) -> pack();
}


##</code><code>##




C(qw/74 97 104 112/);sub C{while(@_){$c**=$C;print
(map{chr($C!=$c?shift:pop)}$_),$C+=@_%2!=1?1:0}}