$whole_file = join ('', <DATA>);
@parts = split /\(.*?\)/, $whole_file;
foreach (@parts) {
    print if $_;
}

__DATA__
(CSW - Q1)
OMIPMS55:NTTCSWQ1:MQSI.3PL846
OMIPMS55:NTTCSWQ1:MQSI.STATUS
OMIPMS55:NTTCSWQ1:MQSI.3PLXDOCK.STATE
(CSW - Q2)
OMIPMS55:NTTCSWQ2:MQSI.3PL846
OMIPMS55:NTTCSWQ2:MQSI.3PL944
(CSW - Q3)
OMIPMS55:NTTCSWQ3:MQSI.3PL846