#My code:
while(<DATA>)
{
#	s/^ou\=.+DC\=/DC\=/i;
	s/.+?(?=DC\=)/DC\=/i;
	print ;

}

__DATA__
OU=NEW HIRES,OU=PBK,DC=VIP-MAIN,DC=ORG
OU=0543 - DR. SMITH PHYSICIANS\, INC,OU=549 VPIU-PARENT - DEPT MANAGED,DC=VIPM,DC=ORG
OU=SYMPH,OU=MANAGED,DC=VIP-MAIN,DC=ORG
OU=USERS,OU=MANAGED,DC=FISC,DC=DS,DC=PPKS,DC=COM
OU=USERS,OU=COVE PA,OU=PEOPLE,DC=ZAPK,DC=PRIV
OU=USER,OU=MANAGED,DC=MINISTERED,DC=NET