I'm not sure what question you are asking, other than the parameter order, but it got me thinking about your statement that tk passes a ref to the callback. At first it didn't strike me as odd, because in perl gtk, all callbacks get $self passed to it as it's first parameter. But then I tried it, and it dosn't in Tk. In Tk a hash exists with the data in it, but it isn't passed by default. The following code demonstartes what I'm talking about. It creates a bunch of "anonymous buttons" and it dosn't pass a ref to the pressed button to the callback sub-routine. The information is available from the hash returned by Tk::widget. Maybe your problem is you think the ref is being passed as an array, but it's actually in an unordered hash. Use the Dumper line to see all that is contained in $caller. Anyways....I learned something today.

#!/usr/bin/perl
use strict;
use Tk;
use Data::Dumper;

my $mw = MainWindow->new;

for(0..4){
$mw->Button(-text => "Hello World$_",
                     -command=>[\&change])->pack;
}
MainLoop;

sub change {
#Tk dosn't pass it's widget reference in callbacks 
#Only the bind() method will implicity pass a widget reference, and ev
+en 
#this default (and generally preferred) action can be defeated. 
#use the widget
 
my $caller = $Tk::widget;
#print Dumper([$caller]); 
print "$caller   ";
print $caller->{'_TkValue_'},'     ';
my $text = $caller->cget('-text');
print "$text\n";
$caller->configure(-text=>"Hello Stranger");
}
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