Use q{}. Just don't go eval'ing it.

my $SQL1=q{SELECT
    to_char(pp.SUBMITTIME, 'YYYY-MM-DD HH:MM:SS') SUBMITTIME,
    to_char(pp.QUEUETIME, 'YYYY-MM-DD HH:MM:SS') QUEUETIME,
    to_char(pp.PREPTIME, 'YYYY-MM-DD HH:MM:SS') PREPTIME,
    to_char(pp.STARTTIME, 'YYYY-MM-DD HH:MM:SS') STARTTIME,
    to_char(pe.ENDTIME, 'YYYY-MM-DD HH:MM:SS') ENDTIME,
    (DATE_PART('second', pe.ENDTIME - pp.STARTTIME )) Seconds_Executio
+n,
    pp.SESSIONID,
    pp.PLANID,
    sp.SESSIONUSERNAME,
    pp.ESTIMATEDCOST,
    pp.ESTIMATEDDISK,
    pp.ESTIMATEDMEM,
    pp.TOTALSNIPPETS,
    pe.RESULTROWS,
    pp.NPSID,
    pp.NPSINSTANCEID,
    pp.OPID,
    pp.LOGENTRYID
from
    $hist_nps_1 ns,
    $hist_session_prolog_1 sp,
    $hist_plan_prolog_1 pp,
    $hist_plan_epilog_1 pe
where
    ns.NPSID = pp.NPSID
and ns.NPSID = pe.NPSID
and ns.NPSID = sp.NPSID
and sp.SESSIONID = pp.SESSIONID
and sp.SESSIONID = pe.SESSIONID
and pp.OPID = pe.OPID
and pp.SUBMITTIME between $StartTime and $EndTime
order by
    pp.SUBMITTIME};
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