3 =head1 F<regen/op_private>
5 This file contains all the definitions of the meanings of the flags in the
6 op_private field of an OP.
8 After editing this file, run C<make regen>. This will generate/update data
14 C<B::Op_private> holds three global hashes, C<%bits>, C<%defines>,
15 C<%labels>, which hold roughly the same information as found in this file
18 F<opcode.h> gains a series of C<OPp*> defines, and a few static data
21 C<PL_op_private_valid> defines, per-op, which op_private bits are legally
22 allowed to be set. This is a good first place to look to see if an op has
23 any spare private bits.
25 C<PL_op_private_bitdef_ix>, C<PL_op_private_bitdefs>,
26 C<PL_op_private_labels>, C<PL_op_private_bitfields>,
27 C<PL_op_private_valid> contain (in a compact form) the data needed by
28 Perl_do_op_dump() to dump the op_private field of an op.
30 This file actually contains perl code which is run by F<regen/opcode.pl>.
31 The basic idea is that you keep calling addbits() to add definitions of
32 what a particular bit or range of bits in op_private means for a
33 particular op. This can be specified either as a 1-bit flag or a 1-or-more
34 bit bit field. Here's a general example:
37 7 => qw(OPpLVAL_INTRO LVINTRO),
38 6 => qw(OPpLVAL_DEFER LVDEFER),
40 mask_def => 'OPpDEREF',
49 Here for the op C<aelem>, bits 6 and 7 (bits are numbered 0..7) are
50 defined as single-bit flags. The first string following the bit number is
51 the define name that gets emitted in F<opcode.h>, and the second string is
52 the label, which will be displayed by F<Concise.pm> and Perl_do_op_dump()
53 (as used by C<perl -Dx>).
55 If the bit number is actually two numbers connected with '..', then this
56 defines a bit field, which is 1 or more bits taken to hold a small
57 unsigned integer. Instead of two string arguments, it just has a single
58 hash ref argument. A bit field allows you to generate extra defines, such
59 as a mask, and optionally allows you to define an enumeration, where a
60 subset of the possible values of the bit field are given their own defines
61 and labels. The full syntax of this hash is explained further below.
63 Note that not all bits for a particular op need to be added in a single
64 addbits() call; they accumulate. In particular, this file is arranged in
65 two halves; first, generic flags shared by multiple ops are added, then
66 in the second half, specific per-op flags are added, e.g.
68 addbits($_, 7 => qw(OPpLVAL_INTRO LVINTRO)) for qw(pos substr vec ...);
73 4 => qw(OPpSUBSTR_REPL_FIRST REPL1ST),
77 (although the dividing line between these two halves is somewhat
78 subjective, and is based on whether "OPp" is followed by the op name or
81 There are some utility functions for generating a list of ops from
82 F<regen/opcodes> based on various criteria. These are:
84 ops_with_check('ck_foo')
86 ops_with_arg(N, 'XYZ')
88 which respectively return a list of op names where:
90 field 3 of regen/opcodes specifies 'ck_foo' as the check function;
91 field 4 of of regen/opcodes has flag or type 'X' set;
92 argument field N of of regen/opcodes matches 'XYZ';
96 addbits($_, 4 => qw(OPpTARGET_MY TARGMY)) for ops_with_flag('T');
98 If a label is specified as '-', then the flag or bit field is not
99 displayed symbolically by Concise/-Dx; instead the bits are treated as
100 unrecognised and are included in the final residual integer value after
101 all recognised bits have been processed (this doesn't apply to individual
104 Here is a full example of a bit field hash:
107 mask_def => 'OPpFOO_MASK',
108 baseshift_def => 'OPpFOO_SHIFT',
109 bitcount_def => 'OPpFOO_BITS',
118 The optional C<*_def> keys cause defines to be emitted that specify
119 useful values based on the bit range (5 to 6 in this case):
121 mask_def: a mask that will extract the bit field
122 baseshift_def: how much to shift to make the bit field reach bit 0
123 bitcount_def: how many bits make up the bit field
125 The example above will generate
127 #define OPpFOO_MASK 0x60
128 #define OPpFOO_SHIFT 5
129 #define OPpFOO_BITS 2
131 The optional enum list specifies a set of defines and labels for (possibly
132 a subset of) the possible values of the bit field (which in this example
133 are 0,1,2,3). If a particular value matches an enum, then it will be
134 displayed symbolically (e.g. 'C'), otherwise as a small integer. The
135 defines are suitably shifted. The example above will generate
137 #define OPpFOO_A 0x20
138 #define OPpFOO_B 0x40
139 #define OPpFOO_C 0x60
141 So you can write code like
143 if ((o->op_private & OPpFOO_MASK) == OPpFOO_C) ...
145 The optional 'label' key causes Concise/-Dx output to prefix the value
146 with C<LABEL=>; so in this case it might display C<FOO=C>. If the field
147 value is zero, and if no label is present, and if no enum matches, then
148 the field isn't displayed.
159 # ====================================================================
161 # GENERIC OPpFOO flags
163 # Flags where FOO is a generic term (like LVAL), and the flag is
164 # shared between multiple (possibly unrelated) ops.
170 # The lower few bits of op_private often indicate the number of
171 # arguments. This is usually set by newUNOP() and newLOGOP (to 1),
172 # by newBINOP() (to 1 or 2), and by ck_fun() (to 1..15).
174 # These values are sometimes used at runtime: in particular,
175 # the MAXARG macro extracts out the lower 4 bits.
177 # Some ops encroach upon these bits; for example, entersub is a unop,
178 # but uses bit 0 for something else. Bit 0 is initially set to 1 in
179 # newUNOP(), but is later cleared (in ck_rvconst()), when the code
180 # notices that this op is an entersub.
182 # The important thing below is that any ops which use MAXARG at
183 # runtime must have all 4 bits allocated; if bit 3 were used for a new
184 # flag say, then things could break. The information on the other
185 # types of op is for completeness (so we can account for every bit
188 my (%maxarg, %args0, %args1, %args2, %args3, %args4);
190 # these are the functions which currently use MAXARG at runtime
191 # (i.e. in the pp() functions). Thus they must always have 4 bits
193 $maxarg{$_} = 1 for qw(
194 binmode bless caller chdir close enterwrite eof exit fileno getc
195 getpgrp gmtime index mkdir rand reset setpgrp sleep srand sysopen
199 # find which ops use 0,1,2,3 or 4 bits of op_private for arg count info
201 $args0{$_} = 1 for qw(entersub); # UNOPs that usurp bit 0
204 qw(reverse), # ck_fun(), but most bits stolen
205 qw(mapstart grepstart), # set in ck_fun, but
206 # cleared in ck_grep,
207 # unless there is an error
208 grep !$maxarg{$_} && !$args0{$_},
209 ops_with_flag('1'), # UNOP
210 ops_with_flag('+'), # UNOP_AUX
211 ops_with_flag('%'), # BASEOP/UNOP
212 ops_with_flag('|'), # LOGOP
213 ops_with_flag('-'), # FILESTATOP
214 ops_with_flag('}'), # LOOPEXOP
215 ops_with_flag('.'), # METHOP
220 grep !$maxarg{$_} && !$args0{$_} && !$args1{$_},
221 ops_with_flag('2'), # BINOP
222 # this is a binop, but special-cased as a
223 # baseop in regen/opcodes
227 $args3{$_} = 1 for grep !$maxarg{$_} && !$args0{$_}
228 && !$args1{$_} && !$args2{$_},
229 # substr starts off with 4 bits set in
230 # ck_fun(), but since it never has more than 7
231 # args, bit 3 is later stolen
234 $args4{$_} = 1 for keys %maxarg,
235 grep !$args0{$_} && !$args1{$_}
236 && !$args2{$_} && !$args3{$_},
237 ops_with_check('ck_fun'),
238 # these other ck_*() functions call ck_fun()
239 ops_with_check('ck_exec'),
240 ops_with_check('ck_glob'),
241 ops_with_check('ck_index'),
242 ops_with_check('ck_join'),
243 ops_with_check('ck_lfun'),
244 ops_with_check('ck_open'),
245 ops_with_check('ck_select'),
246 ops_with_check('ck_stringify'),
247 ops_with_check('ck_tell'),
248 ops_with_check('ck_trunc'),
252 for (sort keys %args1) {
253 addbits($_, '0..0' => {
254 mask_def => 'OPpARG1_MASK',
260 for (sort keys %args2) {
261 addbits($_, '0..1' => {
262 mask_def => 'OPpARG2_MASK',
268 for (sort keys %args3) {
269 addbits($_, '0..2' => {
270 mask_def => 'OPpARG3_MASK',
276 for (sort keys %args4) {
277 addbits($_, '0..3' => {
278 mask_def => 'OPpARG4_MASK',
287 # if NATIVE_HINTS is defined, op_private on cops holds the top 8 bits
288 # of PL_hints, although only bits 6 & 7 are officially used for that
289 # purpose (the rest ought to be masked off). Bit 5 is set separately
291 for (qw(nextstate dbstate)) {
293 5 => qw(OPpHUSH_VMSISH HUSH),
298 # op is in local context, or pad variable is being introduced, e.g.
302 addbits($_, 7 => qw(OPpLVAL_INTRO LVINTRO))
303 for qw(gvsv rv2sv rv2hv rv2gv rv2av aelem helem aslice
304 hslice delete padsv padav padhv enteriter entersub padrange
305 pushmark cond_expr refassign lvref lvrefslice lvavref multideref),
306 'list', # this gets set in my_attrs() for some reason
313 # in constructs like my $x; ...; $x = $a + $b,
314 # the sassign is optimised away and OPpTARGET_MY is set on the add op
316 # Note that OPpTARGET_MY is mainly used at compile-time. At run time,
317 # the pp function just updates the SV pointed to by op_targ, and doesn't
318 # care whether that's a PADTMP or a lexical var.
320 # Some comments about when its safe to use T/OPpTARGET_MY.
322 # Safe to set if the ppcode uses:
323 # tryAMAGICbin, tryAMAGICun, SETn, SETi, SETu, PUSHn, PUSHTARG, SETTARG,
324 # SETs(TARG), XPUSHn, XPUSHu,
325 # but make sure set-magic is invoked separately for SETs(TARG) (or change
328 # Unsafe to set if the ppcode uses dTARG or [X]RETPUSH[YES|NO|UNDEF]
330 # Only the code paths that handle scalar rvalue context matter. If dTARG
331 # or RETPUSHNO occurs only in list or lvalue paths, T is safe.
333 # lt and friends do SETs (including ncmp, but not scmp or i_ncmp)
335 # Additional mode of failure: the opcode can modify TARG before it "used"
336 # all the arguments (or may call an external function which does the same).
337 # If the target coincides with one of the arguments ==> kaboom.
339 # pp.c pos substr each not OK (RETPUSHUNDEF)
340 # ref not OK (RETPUSHNO)
341 # trans not OK (target is used for lhs, not retval)
342 # ucfirst etc not OK: TMP arg processed inplace
343 # quotemeta not OK (unsafe when TARG == arg)
344 # pack - unknown whether it is safe
345 # sprintf: is calling do_sprintf(TARG,...) which can act on TARG
346 # before other args are processed.
348 # Suspicious wrt "additional mode of failure" (and only it):
349 # schop, chop, postinc/dec, bit_and etc, negate, complement.
351 # Also suspicious: 4-arg substr, sprintf, uc/lc (POK_only), reverse, pack.
353 # substr/vec: doing TAINT_off()???
356 # readline - unknown whether it is safe
357 # match subst not OK (dTARG)
358 # grepwhile not OK (not always setting)
359 # join not OK (unsafe when TARG == arg)
361 # concat - pp_concat special-cases TARG==arg to avoid
362 # "additional mode of failure"
365 # mapwhile flip caller not OK (not always setting)
368 # backtick glob warn die not OK (not always setting)
369 # warn not OK (RETPUSHYES)
370 # open fileno getc sysread syswrite ioctl accept shutdown
371 # ftsize(etc) readlink telldir fork alarm getlogin not OK (RETPUSHUNDEF)
372 # umask select not OK (XPUSHs(&PL_sv_undef);)
373 # fileno getc sysread syswrite tell not OK (meth("FILENO" "GETC"))
374 # sselect shm* sem* msg* syscall - unknown whether they are safe
375 # gmtime not OK (list context)
377 # Suspicious wrt "additional mode of failure": warn, die, select.
380 addbits($_, 4 => qw(OPpTARGET_MY TARGMY))
381 for ops_with_flag('T'),
382 # This flag is also used to indicate matches against implicit $_,
383 # where $_ is lexical; e.g. my $_; ....; /foo/
384 qw(match subst pushre trans transr);
391 # op_targ carries a refcount
392 addbits($_, 6 => qw(OPpREFCOUNTED REFC))
393 for qw(leave leavesub leavesublv leavewrite leaveeval);
397 # Do not copy return value
398 addbits($_, 7 => qw(OPpLVALUE LV)) for qw(leave leaveloop);
402 # Pattern coming in on the stack
403 addbits($_, 6 => qw(OPpRUNTIME RTIME))
404 for qw(match subst substcont qr pushre);
408 # autovivify: Want ref to something
409 for (qw(rv2gv rv2sv padsv aelem helem entersub)) {
410 addbits($_, '4..5' => {
411 mask_def => 'OPpDEREF',
423 # Defer creation of array/hash elem
424 addbits($_, 6 => qw(OPpLVAL_DEFER LVDEFER)) for qw(aelem helem multideref);
428 addbits($_, 2 => qw(OPpSLICEWARNING SLICEWARN)) # warn about @hash{$scalar}
429 for qw(rv2hv rv2av padav padhv hslice aslice);
433 # XXX Concise seemed to think that OPpOUR_INTRO is used in rv2gv too,
434 # but I can't see it - DAPM
435 addbits($_, 6 => qw(OPpOUR_INTRO OURINTR)) # Variable was in an our()
436 for qw(gvsv rv2sv rv2av rv2hv enteriter split);
440 # We might be an lvalue to return
441 addbits($_, 3 => qw(OPpMAYBE_LVSUB LVSUB))
442 for qw(aassign rv2av rv2gv rv2hv padav padhv aelem helem aslice hslice
443 av2arylen keys rkeys kvaslice kvhslice substr pos vec multideref);
447 for (qw(rv2hv padhv)) {
448 addbits($_, # e.g. %hash in (%hash || $foo) ...
449 4 => qw(OPpMAYBE_TRUEBOOL BOOL?), # ... cx not known till run time
450 5 => qw(OPpTRUEBOOL BOOL), # ... in void cxt
456 addbits($_, 1 => qw(OPpHINT_STRICT_REFS STRICT))
457 for qw(rv2sv rv2av rv2hv rv2gv multideref);
461 # Treat caller(1) as caller(2)
462 addbits($_, 7 => qw(OPpOFFBYONE +1)) for qw(caller wantarray runcv);
466 # label is in UTF8 */
467 addbits($_, 7 => qw(OPpPV_IS_UTF8 UTF)) for qw(last redo next goto dump);
471 # ====================================================================
473 # OP-SPECIFIC OPpFOO_* flags:
475 # where FOO is typically the name of an op, and the flag is used by a
476 # single op (or maybe by a few closely related ops).
480 addbits($_, 6 => qw(OPpPAD_STATE STATE)) for qw(padav padhv padsv lvavref
481 lvref refassign pushmark);
485 addbits('aassign', 6 => qw(OPpASSIGN_COMMON COMMON));
490 6 => qw(OPpASSIGN_BACKWARDS BKWARD), # Left & right switched
491 7 => qw(OPpASSIGN_CV_TO_GV CV2GV), # Possible optimisation for constants
496 for (qw(trans transr)) {
498 0 => qw(OPpTRANS_FROM_UTF <UTF),
499 1 => qw(OPpTRANS_TO_UTF >UTF),
500 2 => qw(OPpTRANS_IDENTICAL IDENT), # right side is same as left
501 3 => qw(OPpTRANS_SQUASH SQUASH),
502 # 4 is used for OPpTARGET_MY
503 5 => qw(OPpTRANS_COMPLEMENT COMPL),
504 6 => qw(OPpTRANS_GROWS GROWS),
505 7 => qw(OPpTRANS_DELETE DEL),
511 addbits('repeat', 6 => qw(OPpREPEAT_DOLIST DOLIST)); # List replication
515 # OP_ENTERSUB and OP_RV2CV flags
517 # Flags are set on entersub and rv2cv in three phases:
518 # parser - the parser passes the flag to the op constructor
519 # check - the check routine called by the op constructor sets the flag
520 # context - application of scalar/ref/lvalue context applies the flag
522 # In the third stage, an entersub op might turn into an rv2cv op (undef &foo,
523 # \&foo, lock &foo, exists &foo, defined &foo). The two places where that
524 # happens (op_lvalue_flags and doref in op.c) need to make sure the flags do
525 # not conflict, since some flags with different meanings overlap between
526 # the two ops. Flags applied in the context phase are only set when there
527 # is no conversion of op type.
529 # bit entersub flag phase rv2cv flag phase
530 # --- ------------- ----- ---------- -----
531 # 0 OPpENTERSUB_INARGS context
532 # 1 HINT_STRICT_REFS check HINT_STRICT_REFS check
533 # 2 OPpENTERSUB_HASTARG checki OPpENTERSUB_HASTARG
534 # 3 OPpENTERSUB_AMPER check OPpENTERSUB_AMPER parser
535 # 4 OPpDEREF_AV context
536 # 5 OPpDEREF_HV context OPpMAY_RETURN_CONSTANT parser/context
537 # 6 OPpENTERSUB_DB check OPpENTERSUB_DB
538 # 7 OPpLVAL_INTRO context OPpENTERSUB_NOPAREN parser
540 # NB: OPpHINT_STRICT_REFS must equal HINT_STRICT_REFS
543 0 => qw(OPpENTERSUB_INARGS INARGS), # Lval used as arg to a sub
544 1 => qw(OPpHINT_STRICT_REFS STRICT), # 'use strict' in scope
545 2 => qw(OPpENTERSUB_HASTARG TARG ), # Called from OP tree
546 3 => qw(OPpENTERSUB_AMPER AMPER), # Used & form to call
547 # 4..5 => OPpDEREF, already defined above
548 6 => qw(OPpENTERSUB_DB DBG ), # Debug subroutine
549 # 7 => OPpLVAL_INTRO, already defined above
552 # note that some of these flags are just left-over from when an entersub
553 # is converted into an rv2cv, and could probably be cleared/re-assigned
556 1 => qw(OPpHINT_STRICT_REFS STRICT), # 'use strict' in scope
557 2 => qw(OPpENTERSUB_HASTARG TARG ), # If const sub, return the const
558 3 => qw(OPpENTERSUB_AMPER AMPER ), # Used & form to call
560 5 => qw(OPpMAY_RETURN_CONSTANT CONST ),
561 6 => qw(OPpENTERSUB_DB DBG ), # Debug subroutine
562 7 => qw(OPpENTERSUB_NOPAREN NO() ), # bare sub call (without parens)
567 #foo() called before sub foo was parsed */
568 addbits('gv', 5 => qw(OPpEARLY_CV EARLYCV));
572 # 1st arg is replacement string */
573 addbits('substr', 4 => qw(OPpSUBSTR_REPL_FIRST REPL1ST));
578 # bits 0..6 hold target range
581 mask_def => 'OPpPADRANGE_COUNTMASK',
582 bitcount_def => 'OPpPADRANGE_COUNTSHIFT',
584 # 7 => OPpLVAL_INTRO, already defined above
589 for (qw(aelemfast aelemfast_lex)) {
600 2 => qw(OPpDONT_INIT_GV NOINIT), # Call gv_fetchpv with GV_NOINIT
601 # (Therefore will return whatever is currently in
602 # the symbol table, not guaranteed to be a PVGV)
603 6 => qw(OPpALLOW_FAKE FAKE), # OK to return fake glob
609 2 => qw(OPpITER_REVERSED REVERSED),# for (reverse ...)
610 3 => qw(OPpITER_DEF DEF), # 'for $_' or 'for my $_'
612 addbits('iter', 2 => qw(OPpITER_REVERSED REVERSED));
617 1 => qw(OPpCONST_NOVER NOVER), # no 6;
618 2 => qw(OPpCONST_SHORTCIRCUIT SHORT), # e.g. the constant 5 in (5 || foo)
619 3 => qw(OPpCONST_STRICT STRICT), # bareword subject to strict 'subs'
620 4 => qw(OPpCONST_ENTERED ENTERED), # Has been entered as symbol
621 6 => qw(OPpCONST_BARE BARE), # Was a bare word (filehandle?)
626 # Range arg potentially a line num. */
627 addbits($_, 6 => qw(OPpFLIP_LINENUM LINENUM)) for qw(flip flop);
631 # Guessed that pushmark was needed. */
632 addbits('list', 6 => qw(OPpLIST_GUESSED GUESSED));
636 # Operating on a list of keys
637 addbits('delete', 6 => qw(OPpSLICE SLICE));
638 # also 7 => OPpLVAL_INTRO, already defined above
642 # Checking for &sub, not {} or [].
643 addbits('exists', 6 => qw(OPpEXISTS_SUB SUB));
648 0 => qw(OPpSORT_NUMERIC NUM ), # Optimized away { $a <=> $b }
649 1 => qw(OPpSORT_INTEGER INT ), # Ditto while under "use integer"
650 2 => qw(OPpSORT_REVERSE REV ), # Reversed sort
651 3 => qw(OPpSORT_INPLACE INPLACE), # sort in-place; eg @a = sort @a
652 4 => qw(OPpSORT_DESCEND DESC ), # Descending sort
653 5 => qw(OPpSORT_QSORT QSORT ), # Use quicksort (not mergesort)
654 6 => qw(OPpSORT_STABLE STABLE ), # Use a stable algorithm
659 # reverse in-place (@a = reverse @a) */
660 addbits('reverse', 3 => qw(OPpREVERSE_INPLACE INPLACE));
664 for (qw(open backtick)) {
666 4 => qw(OPpOPEN_IN_RAW INBIN ), # binmode(F,":raw") on input fh
667 5 => qw(OPpOPEN_IN_CRLF INCR ), # binmode(F,":crlf") on input fh
668 6 => qw(OPpOPEN_OUT_RAW OUTBIN), # binmode(F,":raw") on output fh
669 7 => qw(OPpOPEN_OUT_CRLF OUTCR ), # binmode(F,":crlf") on output fh
675 # The various OPpFT* filetest ops
677 # "use filetest 'access'" is in scope:
678 # this flag is set only on a subset of the FT* ops
679 addbits($_, 1 => qw(OPpFT_ACCESS FTACCESS)) for ops_with_arg(0, 'F-+');
681 # all OPpFT* ops except stat and lstat
682 for (grep { $_ !~ /^l?stat$/ } ops_with_flag('-')) {
684 2 => qw(OPpFT_STACKED FTSTACKED ), # stacked filetest,
685 # e.g. "-f" in "-f -x $foo"
686 3 => qw(OPpFT_STACKING FTSTACKING), # stacking filetest.
687 # e.g. "-x" in "-f -x $foo"
688 4 => qw(OPpFT_AFTER_t FTAFTERt ), # previous op was -t
694 addbits($_, 1 => qw(OPpGREP_LEX GREPLEX)) # iterate over lexical $_
695 for qw(mapwhile mapstart grepwhile grepstart);
700 1 => qw(OPpEVAL_HAS_HH HAS_HH ), # Does it have a copy of %^H ?
701 2 => qw(OPpEVAL_UNICODE UNI ),
702 3 => qw(OPpEVAL_BYTES BYTES ),
703 4 => qw(OPpEVAL_COPHH COPHH ), # Construct %^H from COP hints
704 5 => qw(OPpEVAL_RE_REPARSING REPARSE), # eval_sv(..., G_RE_REPARSING)
709 # These must not conflict with OPpDONT_INIT_GV or OPpALLOW_FAKE.
710 # See pp.c:S_rv2gv. */
712 0 => qw(OPpCOREARGS_DEREF1 DEREF1), # Arg 1 is a handle constructor
713 1 => qw(OPpCOREARGS_DEREF2 DEREF2), # Arg 2 is a handle constructor
714 #2 reserved for OPpDONT_INIT_GV in rv2gv
715 #4 reserved for OPpALLOW_FAKE in rv2gv
716 6 => qw(OPpCOREARGS_SCALARMOD $MOD ), # \$ rather than \[$@%*]
717 7 => qw(OPpCOREARGS_PUSHMARK MARK ), # Call pp_pushmark
722 addbits('split', 7 => qw(OPpSPLIT_IMPLIM IMPLIM)); # implicit limit
727 2 => qw(OPpLVREF_ELEM ELEM ),
728 3 => qw(OPpLVREF_ITER ITER ),
730 mask_def => 'OPpLVREF_TYPE',
738 #7 => qw(OPpLVAL_INTRO LVINTRO),
739 ) for 'refassign', 'lvref';
743 addbits('multideref',
744 4 => qw(OPpMULTIDEREF_EXISTS EXISTS), # deref is actually exists
745 5 => qw(OPpMULTIDEREF_DELETE DELETE), # deref is actually delete
750 # ex: set ts=8 sts=4 sw=4 et: