I'm quite surprised. I used ActivePerl 5.6.0 back then, but I don't think that the distribution would make any difference. Maybe I'm just mixing this up with something closely related.

perl561delta agrees with me though that ...

Could you provide B::Deparse output of your code for 5.6.0 and 5.6.1? B::Deparse had plenty issues of its own back then, but it will probably be interesting.

lodin

Sure thing. I include a optree dump too (Terse for 5.6.0 since Concise wasn't found.)

(I emptied the body for terseness after making sure it didn't affect the result.)

5.6.0:

>c:\progs\perl560\bin\perl -v

This is perl, v5.6.0 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2001, Larry Wall

Binary build 635 provided by ActiveState Corp. http://www.ActiveState.
+com
Built 15:34:21 Feb  4 2003

...

>c:\progs\perl560\bin\perl -MO=Deparse -e"for my $s ( qw( a b c ) ) {}
+"
foreach my $s ('a', 'b', 'c') {
    ();
}
-e syntax OK

>c:\progs\perl560\bin\perl -MO=Terse -e"for my $s ( qw( a b c ) ) {}"
LISTOP (0x184fcc4) leave [1]
    OP (0x184fca4) enter
    COP (0x184fd10) nextstate
    BINOP (0x184fd4c) leaveloop
        LOOP (0x1828b24) enteriter [1]
            OP (0x184ff6c) null [3]
            UNOP (0x184fe9c) null [141]
                OP (0x184fe7c) pushmark
                SVOP (0x184ff10) const  SPECIAL #0 Nullsv
                SVOP (0x184fec8) const  SPECIAL #0 Nullsv
                SVOP (0x184fe48) const  SPECIAL #0 Nullsv
        UNOP (0x184fd74) null
            LOGOP (0x184fd98) and
                OP (0x1828b8c) iter
                LISTOP (0x184fdc0) lineseq
                    OP (0x184fe28) stub
                    OP (0x1828b6c) unstack
                    COP (0x184fdec) nextstate
-e syntax OK
[download]

5.6.1:

>c:\progs\perl561\bin\perl -v

This is perl, v5.6.1 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2001, Larry Wall

Binary build 635 provided by ActiveState Corp. http://www.ActiveState.
+com
Built 15:34:21 Feb  4 2003

...

>c:\progs\perl561\bin\perl -MO=Deparse -e"for my $s ( qw( a b c ) ) {}
+"
foreach my $s ('a', 'b', 'c') {
    ();
}
-e syntax OK

>c:\progs\perl561\bin\perl -MO=Concise -e"for my $s ( qw( a b c ) ) {}
+"
e  <@> leave[$s:5,7] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 7 -e:1) v ->3
d     <2> leaveloop vK/2 ->e
7        <{> enteriter(next->9 last->d redo->8)[$s:5,7] lK ->b
-           <0> ex-pushmark s ->3
-           <1> ex-list lKPM ->7
3              <0> pushmark sM ->4
4              <$> const(SPECIAL Null)[t2] sM ->5
5              <$> const(SPECIAL Null)[t3] sM ->6
6              <$> const(SPECIAL Null)[t4] sM ->7
-        <1> null vK/1 ->d
c           <|> and(other->8) vK/1 ->d
b              <0> iter s ->c
-              <@> lineseq vK ->-
8                 <0> stub v ->9
9                 <0> unstack v ->a
a                 <;> nextstate(main 7 -e:1) v ->b
-e syntax OK
[download]

A quick look at the docs shows that qw-as-a-list has been around since 5.6.0.

... and my quick look was a bit too quick. Usually the perl5XYdelta documents only document the changes between Perl 5.X.Y and 5.X.0, but perl561delta is an exception. It actually documents the differences between 5.6.1 and 5.005. I've updated my first reply to say 5.6.0 instead of 5.6.1. Hopefully that can be verified. :-)

lodin