The general rule is to use gridForget, reconfigure the widgets in the frame, then regrid everything. This way you reuse a few widgets.

Here is an example using pack, but you should be able to convert to grid.

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

my @stn_init = ( "station1", "station2", "station3" );
my @stn_sup = ("station1", "station2", "station3", "stationa", "statio
+nb" );
my @stn = @stn_init;
my @station_frames;
my @z;
my @w;
my @b;
my @stations;
######################################################################
+###########
$ENV{ TZ } = "PST08PDT07";

use Tk;

my $mw = MainWindow->new;
$mw->minsize( qw(250 150) );
$mw->title( "Metar Watch" );
$mw->configure( -background => 'tan' );

my $menu_bar =
 $mw->Frame( -relief => 'groove', -borderwidth => 3, -background => 'b
+lue', )
 ->pack( '-side' => 'top', -fill => 'x' );

my $file_mb = $menu_bar->Menubutton(
   -text             => 'File',
   -background       => 'blue',
   -activebackground => 'salmon',
   -foreground       => 'white',
)->pack( -side => 'left' );

$file_mb->command(
   -label            => 'About',
   -background       => 'blue',
   -activebackground => 'salmon',
   -command          => \&ABOUT
);

$file_mb->command(
   -label            => 'Exit',
   -background       => 'blue',
   -activebackground => 'salmon',
   -command          => sub { $mw->destroy }
);

my $top = $mw->Scrolled('Pane',
         -scrollbars=>'osoe',
        )->pack( -side => 'top', -fill => 'x' );


# make header
my $header_f= $top->Frame->pack(); 
my $station0 = $header_f->Label( -text => 'Station ', )->pack(-side =>
+ 'left', -pady => 9, -padx => 8 );
my $z0 = $header_f->Label( -text => 'Time (Z)', )->pack(-side => 'left
+', -pady => 9, -padx => 8);
my $w0 = $header_f->Label( -text => 'Wind (KT)', )->pack(-side => 'lef
+t', -pady => 9, -padx => 8);

#make control frame
my $ob_bar =
 $mw->Frame( -relief => 'groove', -borderwidth => 3, -background => 'o
+range', )
 ->pack( '-side' => 'bottom', -fill => 'x' );

my $other_obs=0;
my $ob_lab = $ob_bar->Checkbutton(
   -text       => 'Show more sites',
   -variable   => \$other_obs,
   -foreground => 'black',
   -background => 'orange',
   -command    => \&rebuild
)->pack( -side => 'left' );

my $other_buoys=0;
my $buoy_check = $ob_bar->Checkbutton(
   -text       => 'Show more buoys',
   -variable   => \$other_buoys,
   -foreground => 'black',
   -background => 'orange',
   -command    => \&rebuild
)->pack( -side => 'left' );


&build;

MainLoop;

sub rebuild{

  if($other_obs==1){ @stn = @stn_sup }else{ @stn = @stn_init }

   foreach my $fr (@station_frames){

    my @w = $fr->packSlaves;
     foreach (@w) {$_->packForget;}
    $fr->packForget;
    $mw->update;
   }

&build;

}


sub build {
#make frame for each station
my $n = 0;
for ( 0 .. $#stn ) {
   $station_frames[$_]= $top->Frame->pack(-expand=>1, -fill=>'both');
   $stations[ $n++ ] = $station_frames[$_]->Label( -text => "$stn[$n] 
+" )
             ->pack(-side =>'left', -pady => 1 );

   $z[ $n ] = $station_frames[$_]->Entry(
      -justify     => 'center',
      -background  => 'light yellow',
      -width       => 5,
      -borderwidth => 2,
      -relief      => 'sunken'
   )->pack(-side => 'left', -pady => 2, -padx => 10);

   $w[ $n ] = $station_frames[$_]->Entry(
      -justify     => 'center',
      -background  => 'light green',
      -width       => 7,
      -borderwidth => 2,
      -relief      => 'sunken'
   )->pack(-side => 'left', -pady => 2, -padx => 10);
 
 if($other_buoys==1){
   $b[ $n ] = $station_frames[$_]->Entry(
      -justify     => 'center',
      -background  => 'light green',
      -width       => 7,
      -borderwidth => 2,
      -relief      => 'sunken'
   )->pack(-side => 'left', -pady => 2, -padx => 10);
  }
  
 
 }

$mw->update;
}
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