After some thinking, I came up with the following working solution.

use strict;
use warnings;
use Tk;

my @w;
my $mw = tkinit;
$mw -> geometry("200x200");
    
    our %MyValues=("1",  "term1",
                    "2", "term2",
                    "3",  "term3");

    for my $DBcolumn (1..3) {
            $w[$DBcolumn]=$mw->Entry(-textvariable => \$MyValues{$DBco
+lumn},-justify=>"left",-width => 25)->pack(-side => 'top', -anchor =>
+ 'w');
    }
    my $button1  = $mw->Button(-text => 'Update Values',  -command => 
+\&LoadNewValues)->pack();
    my $button2  = $mw->Button(-text => 'Print Out Content',  -command
+ => \&PrintOutContent)->pack();

MainLoop();

sub PrintOutContent{
    print "$MyValues{1} $MyValues{2} $MyValues{3}\n";
    
}

sub LoadNewValues{
%MyValues=();
%MyValues=("1",  "hallo",
            "2", "ok",
            "3",  "fine");
for my $DBcolumn (1..3) {
    $w[$DBcolumn]->configure(-textvariable=>\$MyValues{$DBcolumn});
}
}
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