Don't try to use a create/destroy cycle to control widgets in Tk. Almost certainly, you will accumulate memory usage with each cycle. Tk is not good about cleaning up after itself( Gtk2 is better, but also is not perfect).

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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