$fullpath = "/$folder";
[download]

my $fullpath ="/$folder";
[download]

It has to do with that thing that I have a hard time describing in my post (see below yours). Since these callbacks are generated within a callback, I don't believe the anonymous subs are eval'ed until the dbclick callback is complete. Since the $fullpath is global to the sub all three callbacks end up with the same value for $fullpath when they are created.

This is why I think using anonymous subs for callbacks is a bad thing - especially when created dynamically like this. Too much potential for action at a distance. I prefer the nice, predictable method of passing an anonymous array to the callback mechanism and letting Tk deal with that. Besides, the fact that the callback then passes the parent widget's ref to the subroutine with this method is immensly useful sometimes. (For example using dynamic callbacks with multiple canvas methods, each of which could use the same callback sub and potential share the same tag name.)

{NULE}
--
http://www.nule.org

The problem is with the way callbacks work in TK. They like to receive an anonymous array with the first element being the sub to be called and subsequent elements are passed to that sub. Here is your code, modified to work.

#!/usr/bin/perl -w

use strict;
use Tk;
use Tk::ROText;

my $mw;     # Main Window
my $fview;  # Text box (Read only)

# Create Main Window and textbox
$mw = new MainWindow;
$fview = $mw->Scrolled( 'ROText',
                        -scrollbars => "oe",
                        -cursor => "hand2"
);
$fview->pack;

# Print "Root" Folder
$fview->insert('end', "\n");
$fview->insert('end', "Root" , "Root");
$fview->insert("Root.last", "\n", "Root_newline");

# Hover over
$fview->tagBind("Root", "<Enter>" =>
                [ \&hover, "Root", 1 ]);
# Hover out
$fview->tagBind("Root", "<Leave>" =>
                [ \&hover, "Root", 0 ]);
# Double click
$fview->tagBind("Root", "<Double-Button-1>" =>
                [ \&dclick, "Root", 0 ]);


# Wait For Christmas!
MainLoop;


# make folder hot!
sub hover
{
    shift;
    my $tag = shift;
    my $do = shift;

    if ($do == 1) {
        $fview->tagConfigure($tag,
                -foreground => "red"
        );
    }
    elsif ($do == 0) {
        $fview->tagConfigure($tag,
                -foreground => "black"
        );
    }
}

# expand folder
sub dclick
{
    shift;
    my $tag = shift;
    my @folders;
    my $fullpath;

    @folders = ( "Linux", "Mail", "Perl" );
    foreach my $folder (@folders) {
        $fullpath = "/$folder";

        # Hover over
        $fview->tagBind($fullpath, "<Enter>" =>
                [ \&hover, $fullpath, 1 ]);
        # Hover out
        $fview->tagBind($fullpath, "<Leave>" =>
                [ \&hover, $fullpath, 0 ]);

        # Diplay the folder link
        $fview->insert( 'Root_newline.last',
                        $folder, $fullpath
        );
        $fview->insert( $fullpath.".last",
                        "\n",
                        $fullpath."_newline"
        );
    }
}
[download]

I conceptually understand why this behaves this way, but words fail me when I try to explain it. Hopefully one of our fellow monks will step up to the plate here. To experiment with callbacks I suggest you do a callback to a sub in this manner (Tk::Canvas style shown here) and have that sub just do this:

$w->bind("tag", '<1>', [ \&bind, "one", "two" ]);
sub stuff
{
    my @a = @_;
    my $i = 0;
    print "Callback received this stuff:\n";
    for (@a) { print "\targ($i) : $_\n"; $i++ }
}
[download]

{NULE}
--
http://www.nule.org

I think I get the general Idea here

Although, not completely, it will suffice enough to let me
continue with my project

Thank You fellow monks!