my @chars6 = ('0'..'9', 'a'..'z', 'A'..'Z', '!','\@', '#', 
  '\$', '\%','^', '&', '\*', '\(', '\)', '<', '>', '\?',
  '`', '\+', '\/', '\[', '\{', '\]','\}', '\|', '=','_',
  '~', ',', '\.');

my $chars6_class = '[' . join( '', @chars6) . ']';

if ($password=~ m/($chars6_class)\1{2}/)
{
  # regenerate password
}

##</code><code>##

m/([[:alnum:]]|[[:punct:]])\1{2}/