pack and place are for positioning subwindows inside a window, they should not matter.

Lacking code from you, here's a small example that puts up a main window and a top level window exactly where they are supposed to be.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11114006
use warnings;
use Tk;

my $mw = MainWindow->new;
$mw->geometry( '300x300+100+300' );

my $top = $mw->Toplevel();
$top->geometry( '300x300+500+300' );

MainLoop;
[download]

Update: As I think about this, I haven't had the need to place a secondary window on the screen at particular x,y screen coordinates. If this window has to be at particular coordinates relative to the main window, why isn't it in the main window? Or why doesn't simple pack() work? The user can move these windows around and "save windows", meaning that you ask each window where it is and save those coordinates. Lot's of possibilities here.

Thank you for bothering to reply. The code below is just a bit of the definition of $G=$mw->DialogBox with most fields initially disabled. $G isn't displayed until requested by action in the main window.

if(not defined $G) {
    $G = $mw->DialogBox(title => "List",
        -buttons => ["Edit/Save", "Add Picture", "Exit"],
        -default_button=>"Exit", -cancel_button=>'Exit',
        -command=>\&handle_display_button);

#       lots of code here

    my $img2 = $mv->Photo('resized');
    $G->Label(-image=>'resized',
            -height=>400,
            -width=>600)->place(-x=>20, -y=>190);
    $lft= $G->Button(-image=>'left',
            -command=>[\&change_picture, 'down'],
             -relief=>'flat')->place(-x=>0, -y=>350);
    $rr = $Gems->Button(-image=>'right',
            -command=>[\&change_picture, 'up'],
            -relief=>'flat')->place(-x=>620, -y=>350);
    $scale = $G->Scale(-from=>0,
            -to=>$#Search_List,
            -variable=>\$sb_idx,
            -command=>\&Change_Record,
            -orient=>'horizontal',
            -length=>540)->place(-x=>50, -y=>600);
        
#    $G->positionfrom('program');
    $G->geometry('650x680+0+0');
#    $G->geometry('+0+0');
    $G->minsize(650,680);
    $G->maxsize(650,680);
}
$G->Show;
[download]

->geometry('650x680); gave it the size I wanted, but it started opening half off screen so I added '+pos+pos', but it didn't change anything, no matter what values I used. Every time it is shown it is always in the same place and I have to move it manually to see it in its entirety.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11114006
use warnings;
use Tk;
use Tk::DialogBox;

my $mw = MainWindow->new;
$mw->geometry( '300x300+600+300' );

my $G = $mw->DialogBox(
  -popover => undef, -popanchor => 'nw', -overanchor => 'nw');
$G->minsize(650,680);
$G->maxsize(650,680);

$mw->Button(-text => 'Open Dialog Box', -command => sub { $G->Show },
  )->pack;

MainLoop;
[download]