#!/bin/perl5

use strict;
use warnings;
use Tk;

my $mw = MainWindow->new(-title => 'bullets');
my $t = $mw->Text->pack;

{   local $/ = undef;
    $t->insert('1.0', <DATA>); }
    
$t->tagConfigure(
  'bullets',
  -lmargin1 => '30',
  -lmargin2 => '61',
);
$mw->Button(-text => 'bullet', -command => \&bullets)->pack;
MainLoop;

sub bullets{
  unless ($t->tagRanges('sel')){
    print "Can't apply bullets - no text selected\n";
    return;
  }
  my $first_index = $t->index('sel.first');
  my $last_index  = $t->index('sel.last');
  my $first_line = line_number($first_index);
  my $last_line = line_number($last_index);
  $t->unselectAll;
  for my $line ($first_line..$last_line){
    $t->GotoLineNumber($line);
    $t->insert("$line.0", "*      ");
  }
  $t->tagAdd('bullets', "$first_index linestart", "$last_index  lineend");
  return;
}

sub line_number{
  my $index = shift;
  my ($line) = $index =~ /^(\d+)\./;
  return $line;
}
__DATA__
Twas brillig, and the slithy toves
Did gyre and gimble in the wabe:
All mimsy were the borogoves,
And the mome raths outgrabe.