I'm probably going to mess this up, but I think what's happening is:

You use \$map_fields[$cnt2] to store the location of (pointer to) the space occupied by $map_fields[$cnt2], but I think that the dereferencing of the array is happening first, so you store a reference to a string which is the value stored at $map_fields[$cnt2].

I think the solution is to initially store references to scalars in @map_fields, then always manipulate them as references, as in: 
use Tk;
$mw = new MainWindow(-title=>'mapp');
$pg = $mw->Frame;

@map_fields = \(qw( A B C D E ));
$cnt2 = 0;
@file_fieldnames =  qw( SHOW COLUMNS FROM lead SKIP );
  
foreach my $field ( @file_fieldnames ) 
{
   $pg->Label(-relief => 'sunken', -width => 15, -text => $field)->pac
+k();
   my $brb = $pg->BrowseEntry(-variable => ($map_fields[$cnt2]) );
   $brb->insert('end', @$dbfields);
   $cnt2++;
   $brb->pack();
}

my $btn =$pg->Button(-text=>'doit', -command => sub { doit() } );
$btn->pack;
$pg->pack();

MainLoop;

sub doit 
{
    $ifg->{parameter} = '1,2,3,4,5';
    my @a = ( split ( ",", $ifg->{parameter} ) );
    for ( @map_fields ) { $$_ = shift @a } ;
}

[download]
This code seems to do what you want, though I didn't learn the grid placment manager or make a DB to truly try it out.

--Bob Niederman, http://bob-n.com

All code given here is UNTESTED unless otherwise stated.

In reply to Re: Updating variables in Tk programmes by bobn
in thread Updating variables in Tk programmes by jdtoronto

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