349         |       USE startsub
 350                         { CvSPECIAL_on(PL_compcv); /* It's a BEGIN {} */ }
 351                 BAREWORD BAREWORD optlistexpr ';'
 352                         {
 353                           SvREFCNT_inc_simple_void(PL_compcv);
 354                           utilize($1, $2, $4, $5, $6);
 355                           parser->parsed_sub = 1;
 356                           $$ = NULL;
 357                         }
##</code><code>##

6307     /* Fake up an import/unimport */
6308     if (arg && arg->op_type == OP_STUB) {
6309         imop = arg;             /* no import on explicit () */
6310     }
##</code><code>##

$ perl -mopen -e 1

$ perl -Mopen -e 1
open: needs explicit list of PerlIO layers at -e line 0.
BEGIN failed--compilation aborted.

##</code><code>##

$ perl -Mopen= -e 1
open: needs explicit list of PerlIO layers at -e line 0.
BEGIN failed--compilation aborted.

$ perl -mopen= -e 1
open: needs explicit list of PerlIO layers at -e line 0.
BEGIN failed--compilation aborted.