#!/usr/bin/perl
use strict;
use warnings;
use Algorithm::Loops 'NestedLoops';
use Win32::OLE;

my $file = $ARGV[0] or die "Usage: $0 <file>";   # Important to use full path

# Win32::OLE Example Program
my $word;
eval {$word = Win32::OLE->GetActiveObject('Word.Application')};
die "MSWord not installed" if $@;
$word = Win32::OLE->new('Word.Application') or die "Can't start Word" if ! defined $word;
$word->{Visible} = 1;

 
my @key = (['a' .. 'z'], [0 .. 9], ['A' .. 'Z'], [0 .. 9]);
my $next = NestedLoops(\@key);

while (my @half = $next->()) {
    my $pass = Gen_Pass(@half);
    my $doc = $word->{Documents}->open({
        'FileName'         => $file,
        'PasswordDocument' => $pass,
    });
    next if ! defined $doc;
    print "$pass\n", last;
} 

sub Gen_Pass {
    my @pass = @_;
    my %conv = (
        1 => '!', 2 => '@', 3 => '#', 4 => '$', 5 => '%',
        6 => '^', 7 => '&', 8 => '$', 9 => '(', 0 => ')',
    );
    my ($third, $first) = @pass[2, 0];
    push @pass, $pass[-1];                   # Duplicate the 4th number
    push @pass, lc substr(++$third, 0, 1);   # Increment 3rd char and lc it  
    push @pass, $conv{$pass[1]};             # Convert 2nd num to a spec char
    push @pass, uc substr(++$first, 0, 1);   # Increment 1st char and uc it  
    return join '', @pass;
}