Tree and HList both support that feature. Look at the documentation for hide and show methods in the documentation for HList, and for the -state => 'normal'. The trick however is that you must call setmode on each node in the tree to set its initial state.

use strict;
use warnings;
use Tk;
use Tk::Tree;

my $main = MainWindow->new(-title => "Demo" );
my $tree = $main->ScrlTree(
    -font       => 'FixedSys 8',
    -itemtype   => 'text',
    -separator  => '/',
    -scrollbars => "se",
    -selectmode => 'single',
);

$tree->pack( -fill => 'both', -expand => 1 );

$tree->add ('root', -text => 'root of all ...', -state => 'normal' );
$tree->add ('root/top 1', -text => 'first top level node', -state => '
+normal' );
$tree->add ('root/top 2', -text => 'second top level node', -state => 
+'normal' );
$tree->add ('root/top 2/nested 1', -text => 'first nested node', -stat
+e => 'normal' );
$tree->add ('root/top 2/nested 2', -text => 'second nested node', -sta
+te => 'normal' );

openTree ($tree);

MainLoop;

sub openTree {
    my $tree = shift;
    my ( $entryPath, $openChildren ) = @_;
    my @children = $tree->info( children => $entryPath );

    return if !@children;

    for (@children) {
        openTree( $tree, $_, 1 );
        $tree->show( 'entry' => $_ ) if $openChildren;
    }
    $tree->setmode( $entryPath, 'close' ) if length $entryPath;
}

sub closeTree {
    my $tree = shift;
    my ( $entryPath, $hideChildren ) = @_;
    my @children = $tree->info( children => $entryPath );

    return if !@children;

    for (@children) {
        closeTree( $tree, $_, 1 );
        $tree->hide( 'entry' => $_ ) if $hideChildren;
    }
    $tree->setmode( $entryPath, 'open' ) if length $entryPath;
}
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