How to reuse a placeholder

I have a query, which needs a date substituting twice. Declaring an intermediate variable seemed the natural way to do this viz:

my $nots = $dbh->selectall_arrayref(<<SQL, {}, $end);
declare \@eom datetime
select \@eom = ?
select ccy.currencyCode Currency,
       swp.loadStatus,
       sum(leg.notionalAmount) Notional,
       count(*) Trades
from   $swap_table swp,
       SWAPFLOATINGLEG leg,
       $reference..CURRENCY ccy
where  swp.terminationDate > \@eom
and    swp.registeredBusinessDay <= \@eom
and    leg.oid = swp.$leg_column
and    ccy.oid = leg.currency
group by ccy.currencyCode, swp.loadStatus
SQL

Unfortunately, this is not being parsed properly, as can be seen from running with DBI_TRACE=1

    <- selectall_arrayref('declare @eom datetime
select @eom = ?
select ccy.currencyCode Currency,
       swp.loadStatus,
       sum(leg.notionalAmount) Notional,
       count(*) Trades  
from   PLAINVANILLASWAP swp,
       SWAPFLOATINGLEG leg,
       REFERENCE_TST2..CURRENCY ccy
where  swp.terminationDate > @eom
and    swp.registeredBusinessDay <= @eom
and    leg.oid = swp.floatingLeg
and    ccy.oid = leg.currency
gro...' HASH(0x8ac34c) ...)= undef at eom_stats.pl line 177
DBD::Sybase::db selectall_arrayref failed: Server message number=7332 severity=15 state=1 line=1 server=SYB_SWPCLR_TST procedure=DBD1 text=The untyped variable ? is allowed only in in a WHERE clause or the SET clause of an UPDATE statement or the VALUES list of an INSERT statement
       ERROR: 7332 'Server message number=7332 severity=15 state=1 line=1 server=SYB_SWPCLR_TST procedure=DBD1 text=The untyped variable ? is allowed only in in a WHERE clause or the SET clause of an UPDATE statement or the VALUES list of an INSERT statement
' (err#0)

...

I could pass in the parameter twice, but I was hoping to be able to reuse the placeholder by declaring an intermediate variable, which works in isql. What am I doing wrong?

Alternatively, is there a syntax in DBI for reusing a placeholder.

Ivor.