# -command => \&callback(time),
 -command => \&callback,
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I'm not going to install Tk at the moment. But, \&callback does not call callback() (it just provides a code ref):

 $ perl -le 'sub callback { die "called( @_ )!" } print \&callback'
CODE(0x219b4c0)
 $ perl -le 'sub callback { die "called( @_ )!" } print \&callback("ar
+g")'
called( arg )! at -e line 1.
 $
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The Tk::Button documentation (see also Tk::callbacks) implies that -command => $codeRef will not immediately call the referenced sub.

There certainly could be other reasons for that usage to cause "pre-mature exit and crash". For example, -command => \&callback, time, would likely "crash".

I see plenty of evidence to suggest that it will not cause callback() to be called at button-creation time and no details suggesting that you have enough evidence to support that one part of your claim.

- tye        

I'm not going to install Tk at the moment.

Ok, thanks for explaining. It's the () that causes premature exiting.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = new MainWindow;
$mw->geometry("400x200");

my $button = $mw->Button(-text    => "Sub test exit",
                 -command => \&callback(),  # exits prematurely
              # -command => \&callback,     # works ok
                          )->pack();

MainLoop;

sub callback{
  print "exiting\n";
  Tk::exit;
}
__END__
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---

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh