I'm sorry I don't currently have access to a database to test this against, but I believe this should work:

my $sth = $dbh->prepare(q~
    select
        smt.uniqueid, smt.creationtime, att.name, att.val, gsm.msisdn
    from
        dagenericsmt smt, dagenericsmtattribute att, dagsmproduct gsm
    where smt.uniqueid = att.genericsmt_uniqueid
        and smt.product_uniqueid = gsm.uniqueid
        and smt.smtstatus=2
        and smt.smtcommand=3
        and att.name in ('GSM/Cur/IMSI','GSM/Rpl/IMSI')
        and smt.acktime is null order by smt.uniqueid
~)
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It's also easier for us (and you) to read if you can split it up and indent it some logical way. :o) Update: (like dragonchild's *beautiful* example below - definitely gets my ++!)