The docs show an example

use strict;
use warnings;
use Tk;
use Tk::widgets qw/CollapsableFrame Pane/;

my $mw = MainWindow->new;

my $pane = $mw->Scrolled(
  qw/Pane -width 250 -height 50 -scrollbars osow -sticky nw/,
)->pack;

my $cf = $pane->CollapsableFrame(-title => 'Frame1 ', -height => 50);
$cf->pack(qw/-fill x -expand 1/);
$cf->toggle;

my $colf = $cf->Subwidget('colf');
my $but = $colf->Button(-text => 'Close Frame 1!');
$but->pack;
$but->bind('<Button-1>' => [sub {$_[1]->close}, $cf]);

MainLoop;
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