#Here's what I tried but it doesnt do what I want
my($text2) = "test_\1_\2_\3";
my($text3) = q{'$text2'};
print "$text3\n";
[download]

... because your first value gets already interpolated. But I guess you should check what is really returned by the widget with Data::Dumper. Did you also try Entry option -textvariable to avoid get()? e.g.

    $zoom_factor_entry = $draw_bar -> Entry (
        "-width" => 2,
        "-textvariable"  => \$zoom_step,
    ) -> pack( "-side" => 'left', "-padx" => 3);
[download]