Are you saying that the example I gave should work ?
When running with DBI_TRACE=4 I get this

-> connect for DBD::Sybase::dr (DBI::dr=HASH(0x1ba63c)~0x10d178 'serve
+r=MY_REPSERVER' 'repserv_user' **** HASH(0x24294))
    New DBI::db (for DBD::Sybase::db, parent=DBI::dr=HASH(0x10d178), i
+d=)
    dbih_setup_handle(DBI::db=HASH(0x10d13c)=>DBI::db=HASH(0x242948), 
+DBD::Sybase::db, 1b8f74, Null!)
    dbih_make_com(DBI::dr=HASH(0x10d178), 2410f8, DBD::Sybase::db, 242
+8, 0) thr#0
    syb_db_login() -> checking for chained transactions
    servermsg_cb -> number=17001 severity=10 state=0 line=0 server=SRS
+_SUNTS_TST text=No SRV_OPTION handler installed.
    clientmsg_cb -> ct_options(): user api layer: external error: An e
+rror was returned from the server while setting theoptions, check the
+ server message for details.
    syb_db_login() -> chained transactions are not supported
    !! ERROR: 183 CLEARED by call to prepare method
    -> prepare for DBD::Sybase::db (DBI::db=HASH(0x10d13c)~0x242948 's
+elect @@version')
    New DBI::st (for DBD::Sybase::st, parent=DBI::db=HASH(0x242948), i
+d=)
    dbih_setup_handle(DBI::st=HASH(0x242a14)=>DBI::st=HASH(0x242a08), 
+DBD::Sybase::st, 242a20, Null!)
    dbih_make_com(DBI::db=HASH(0x242948), 243808, DBD::Sybase::st, 396
+, 0) thr#0
    <- prepare= DBI::st=HASH(0x242a14) at Sybase.pm line 103 via repse
+rv.pl line 11
    -> execute for DBD::Sybase::st (DBI::st=HASH(0x242a14)~0x242a08)
    syb_alloc_cmd() -> CS_COMMAND 260608 for CS_CONNECTION 242c08
    syb_db_opentran() -> ct_command(
BEGIN TRAN DBI243808
) = 1
    syb_db_opentran() -> ct_send() = 1
    servermsg_cb -> number=14024 severity=12 state=0 line=0 server=SRS
+_SUNTS_TST text=Executor does not allow the entered command in the cu
+rrent mode.
[download]

Am I missing something basic ?
I've done this with sybperl (albeit a few years ago) but cannot seem to get this example to work.
Any help appreciated