More information (I made this without realizing I wasn't logged in to PM): I set the stack level trace to trace(6), and got some other messages:

ows: '2895385'
    DBI::db=HASH(0x80a28e4) trace level set to 0x0/6 (DBI @ 0x0/0) in 
+DBI 1.642-ithread (pid 8200)

    -> prepare for DBD::Sybase::db (DBI::db=HASH(0x80a2974)~0x80a28e4 
+'declare @skiprows int, @getrows int; select @skiprows = 0; select @g
+etrows = 10000; set rowcount @skiprows; select * into #debt from debt
+ order by debt_id, debt_no asc; set rowcount @getrows;select * from d
+ebt where (debt_id NOT IN ( select * from #debt ) ) ORDER BY debt_id,
+ debt_no ASC') thr#804d1a0
    New 'DBI::st' (for DBD::Sybase::st, parent=DBI::db=HASH(0x80a28e4)
+, id=undef)
    dbih_setup_handle(DBI::st=HASH(0x80a2f54)=>DBI::st=HASH(0x80a2a24)
+, DBD::Sybase::st, 80a2f14, Null!)
    dbih_make_com(DBI::db=HASH(0x80a28e4), 80b5004, DBD::Sybase::st, 4
+20, 0) thr#804d1a0
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), Err, DBI::db=HASH(0x80a
+28e4)) SCALAR(0x81d0754) (already defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), State, DBI::db=HASH(0x8
+0a28e4)) SCALAR(0x81d07b4) (already defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), Errstr, DBI::db=HASH(0x
+80a28e4)) SCALAR(0x81d0784) (already defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), TraceLevel, DBI::db=HAS
+H(0x80a28e4)) 6 (already defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), FetchHashKeyName, DBI::
+db=HASH(0x80a28e4)) 'NAME_lc' (already defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), HandleSetErr, DBI::db=H
+ASH(0x80a28e4)) undef (not defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), HandleError, DBI::db=HA
+SH(0x80a28e4)) undef (not defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), ReadOnly, DBI::db=HASH(
+0x80a28e4)) undef (not defined)
    dbih_setup_attrib(DBI::st=HASH(0x80a2a24), Profile, DBI::db=HASH(0
+x80a28e4)) undef (not defined)
    syb_st_prepare() -> inUse = 0
    syb_st_prepare() -> set inUse
    <- prepare= ( DBI::st=HASH(0x80a2f54) ) [1 items] at export_debt.p
+l line 52
    -> errstr in DBD::_::common for DBD::Sybase::db (DBI::db=HASH(0x80
+a2974)~0x80a28e4) thr#804d1a0
    <- errstr= ( '' ) [1 items] at export_debt.pl line 63
err
$VAR1 = '';
    -> FIRSTKEY in DBD::_::common for DBD::Sybase::st (DBI::st=HASH(0x
+80a2a24)~INNER) thr#804d1a0
    <- FIRSTKEY= ( undef ) [1 items] at /usr/lib/perl5/site_perl/5.28.
+2/i686-linux-thread-multi/Data/Dumper.pm line 232 via  at /usr/lib/pe
+rl5/site_perl/5.28.2/i686-linux-thread-multi/Data/Dumper.pm line 604
query
$VAR1 = bless( {}, 'DBI::st' );
    -> execute for DBD::Sybase::st (DBI::st=HASH(0x80a2f54)~0x80a2a24)
+ thr#804d1a0
    syb_alloc_cmd() -> CS_COMMAND 85ebd90 for CS_CONNECTION 85a5060
    cmd_execute() -> ct_command() OK
    cmd_execute() -> ct_send() OK
    cmd_execute() -> set inUse flag
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