If you're wondering what regex mean, try YAPE::Regex::Explain

use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(
qr/.*(\d{6,8}).*/ )->explain,"\n";
__END__
The regular expression:

(?-imsx:.*(\d{6,8}).*)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    \d{6,8}                  digits (0-9) (between 6 and 8 times
                             (matching the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

To see what is happening, try

use re 'debug';