The routine want's a coderef. In the first case you're giving it one. It is a reference to a routine which, when executed, calls change_mode(1).

In the second case you're giving it the result of calling a subroutine whose reference is held in $change_mode.

And the third case is the same as the second, the except dereferencing is done with different symbols. 

#!/usr/bin/perl -w

use Data::Dumper;
$Data::Dumper::Deparse = 1;

my $change_mode = \&change_mode;

sub change_mode { return "returning: @_ " }

#Case 1:  Callback routine called directly with anonymous reference
Button(-text => 'To Lower Case',
             -command => sub { &change_mode(1) }
             );

#Case 2:  Callback routine called with argument via named reference ve
+r. 1      
Button(-text => 'To Upper Case',
             -command => &{$change_mode}(2)
             );

#Case 3:  Callback routine called with argument via named reference ve
+r. 2      
Button(-text => 'To Mixed Case',
             -command => $change_mode->(3)
             );

sub Button
{
    my %h = @_;
    print Dumper(\%h);
}

[download]
Result: 
$VAR1 = {
          '-text' => 'To Lower Case',
          '-command' => sub {
                                &change_mode(1);
                            }
        };
$VAR1 = {
          '-text' => 'To Upper Case',
          '-command' => 'returning: 2 '
        };
$VAR1 = {
          '-text' => 'To Mixed Case',
          '-command' => 'returning: 3 '
        };

[download]
--Bob Niederman, http://bob-n.com

In reply to Re: Passing arguments to callback routines with named references by bobn
in thread Passing arguments to callback routines with named references by nysus

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