What is this line doing in the perl script?

[anakin30]

hie there

can someone help me

i have this line as input file

CN=[e-mail],CN=ExternalContacts,DC=dhl,DC=com

whats is this line doing with the input above

(($this_mail) = ($this_in =~ /CN=(.*),CN=ExternalContacts/gio));

This is the line in input file

CN=[e-mail],CN=ExternalContacts,DC=dhl,DC=com

This is the perl script if you need to refer

  open( IN, "$INFILE" );
  while( $this_in = <IN> )
  {
    if ($this_in =~ /^dn: /gio)
    {
      (($this_mail) = ($this_in =~ /CN=(.*),CN=ExternalContacts/gio));
      $this_user = $conn_in->search(base => $ldapopts_root, scope => "
+sub", filter => "(|(mail=$this_mail)(mailAlternateAddress=$this_mail)
+)", attrs => ['uid','mail','mailalternateaddress','cn','ou']);
      &Debug( 3, "Search:(|(mail=$this_mail)(mailAlternateAddress=$thi
+s_mail))");

      if ($this_user->entries)
      {
        foreach $my_entry ($this_user->entries)
        {
          $entry_uid = $my_entry->get_value('uid');
          $entry_mail = $my_entry->get_value('mail');
          @all_alts = $my_entry->get_value('mailalternateaddress');
          $my_alt_all = "";
          foreach $entry_alt (@all_alts)
          {
            $my_alt_all .= $entry_alt;
            $my_alt_all .= ",";
          }
          chop($my_alt_all);
          $entry_cn = $my_entry->get_value('cn');
          $entry_ou = $my_entry->get_value('ou');
          &Debug( 3, "$entry_ou|$entry_uid|$entry_mail|$my_alt_all|$en
+try_cn");
        }
      }
       elsif ($this_in =~ /deutschepost/gio)
      {
        chop($this_in);
        &Debug( 2, "$this_in");
        &Debug( 2, "changetype: delete\n");
      }
       else
      {
        (($this_mail1) = ($this_mail =~ /\@(.*)/gio));
        &Debug( 1, "$this_mail1");
      }
    }
  }