that is easy.

$/="";
while (<DATA>)
{
    /^([^,]+,[0-9]+)/;
    $a = $1;
    
    @a = /(CN=[^,"]+)/msg;
    print qq($a,"), join(", ", @a), qq("\n\n);

}
__DATA__
DHCP Administrators,2,"CN=May Mary,OU=Enterprise Admins,Users,DC=INTER
+NETNET,DC=com
Domain Admins,Users,DC=INTERNETNETCOM,DC=com",,

DnsAdmins,2,"Enterprise Admins,Users,DC=INTERNETNET,DC=com
CN=Arth Gure,OU=Marketing,OU=User Accounts,DC=INTERNETNET,DC=com
Domain Admins,Users,DC=INTERNETCOM,DC=com",,

AS400 Query Database,2,"CN=Joe Car,OU=Systems/Operations,OU=MIS,OU=Use
+r Accounts,DC=INTERNETNET,DC=com
CN=Ricrad Tallar,OU=Systems/Operations,OU=MIS,OU=User Accounts,DC=INTE
+RNETNETCOM,DC=com",,

Deptpar Access,8,"CN=John Class,OU=Marketing,OU=User Accounts,DC=INTER
+NETNET,DC=com
CN=Judy Lipa,OU=Marketing,OU=User Accounts,DC=INTERNETNET,DC=com
CN=George Grey,OU=Marketing,OU=User Accounts,DC=INTERNETNET,DC=com
Artur More,OU=Marketing,OU=User Accounts,DC=INTERNETNET,DC=com
CN=Raimun Sirilo,OU=Executive,OU=User Accounts,DC=INTERNETNET,DC=com
CN=Amilcar Ove,OU=Marketing,OU=User Accounts,DC=INTERNETNET,DC=com
Daniel Santos,OU=Executive,OU=User Accounts,DC=INTERNETNET,DC=com
CN=Paula Corte,OU=Executive,OU=User Accounts,DC=INTERNETNET,DC=com"

Human_Resources,3,"CN=Katarine Gilly,OU=Executive,OU=User Accounts,DC=
+INTERNETNET,DC=com
CN=Chris Head,OU=Human Resources,OU=Finance & Administration,OU=User A
+ccounts,DC=INTERNETNET,DC=com
CN=Susany Cadru,OU=Human Resources,OU=Finance & Administration,OU=User
+ Accounts,DC=INTERNETNET,DC=com"
[download]

Output:

DHCP Administrators,2,"CN=May Mary"

DnsAdmins,2,"CN=Arth Gure"

AS400 Query Database,2,"CN=Joe Car, CN=Ricrad Tallar"

Deptpar Access,8,"CN=John Class, CN=Judy Lipa, CN=George Grey, CN=Raim
+un Sirilo, CN=Amilcar Ove, CN=Paula Corte"

Human_Resources,3,"CN=Katarine Gilly, CN=Chris Head, CN=Susany Cadru"
[download]

hint:
if one regex gets to complicated: split it up.