#!/usr/bin/perl

# http://perlmonks.org/?node_id=1213205

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

my $mw = MainWindow->new( -bg=> "#000000", -borderwidth=> 0); 
$mw->geometry( '1000x600' );

my $LB = $mw->Scrolled ( 'ROText',
            -bg => '#C0C0C0', 
            -fg => '#000000', 
            -selectforeground => '#000000', 
            -selectbackground => '#C0C0C0',
            -font => 'Courier 16 normal', 
            -relief => 'groove', 
            -cursor => 'top_left_arrow',
            -scrollbars => 'e',
        )->pack( -side => 'right', -expand => 1, -fill => 'both', );

sub selectAccount {
    my $this = shift;
    print "select: $this\n";
    $LB->tagConfigure("A$_", -background => 'grey') for 1..200;
    $LB->tagConfigure("A$this", -background => 'yellow');
}
sub markAccount {
    my $this = shift;
    print "mark: $this\n";
    my $fontref = $LB->tagCget("A$this", -font);
    my $font = $fontref ? $$fontref : 'Courier 16 normal';
    my $new = $font =~ /normal/ ? 'Courier 16 bold' : 'Courier 16 norm
+al';
    $LB->tagConfigure("A$this", -font => $new);
    
}
sub InitializeListBox {
    $LB->delete('1.0','end');
    #for (my $i=1; $i<200; $i++) {
    for my $i (1..200) {
        $LB->insert('end', $i x 10, "A$i" );
        $LB->tag( 'bind', "A$i", '<Button-1>'  => sub { selectAccount(
+$i) } );
        $LB->tag( 'bind', "A$i", '<Double-1>'  => sub { markAccount($i
+) } );
        $LB->insert('end', "\n" );
     }
}

InitializeListBox();

MainLoop;
[download]

Why your code sub { selectAccount(+$i) } works?
And why my code sub { &selectAccount(+$i) } did not?
... I have always been using with the ampersand with binds.

Further to tybalt89's reply...
The  & (ampersand) has nothing to do with it. (Likewise the  + (plus) sign in front of the $i; I don't know where that came from.) The trick is to switch from your C-style  for (my $i=1; $i<200; $i++) { ... } loop to a Perl-style  for my $i (1..200) { ... } loop.

In the C-style loop, the variable  $i is defined once and given many values, the last of which is 200 (because that's the value that finally fails the  $i<200 test). All the  sub { selectAccount($i) } and  sub { markAccount($i) } expressions symbolicly reference (if that's the right term) this single  $i variable which has only one final value. At the end of the  InitializeListBox() routine, the referential bindings "close" over the single  $i variable (with its single value) because all symbolic references to the variable are used within code references which are passed to another subroutine, tag(), and must therefore persist. (Again, I may not have quite the right terminology here, but that's the general idea.)

In the Perl-style loop, the  $i variable is aliased to many different values. Each  sub { ... } expression symbolically references a different value via the  $i alias. All these different, individual values are then closed over. I think that's about right.

See closure.

As to your other, Tk-related questions, it's been a while since I've played with Tk very much and someone else could, I'm sure, give you much better answers with much less mental effort.

Update: Made a few minor changes to wording in the interest, I hope, of clarity.

I actually never used any perl style loops before other than foreach my $i ( ... );
and the working script I took that code indeed used foreach statement.

I got alot of recoding work to do, replacing all C style loops with a Perl style loop. Thanks for clarification.

Never use & except in one very special rare case.

The real fix was using for my $i (1..200) { instead of the C style for(;;).