Unfortunately in Perl 5.6.1 it seems that keys comes off in a different order for lexical and global hashes (with anonymous hashes coming off in the same order as global).

Unfortunately in Perl 5.6.1 it seems that keys comes off in a different order for lexical and global hashes

That's an interesting and unexpected observation. Do you have an example?

Abigail

Anonymonks observation is both strange and true. The following shows the results from AS 5.6.1 and 5.8 with ari/buk using an our'd hash and buk2 using a my'd hash.

#! perl -slw
use strict;
use vars qw[@a @b @c @d];
use Benchmark 'cmpthese';

our @a=1..10; our @b=5..15; our @c=10..20; our @d=15..25;
our (@A, @B, @C);

my $ari = '@A = keys %{{ map +($_ => undef), @a, @b, @c, @d }};';
my $buk = '@B = do{local %h; ++@h{@a,@b,@c,@d}; keys %h};';
my $buk2= '@C = do{   my %h; ++@h{@a,@b,@c,@d}; keys %h};';

cmpthese( -1, { ari=>$ari, buk=>$buk, buk2=>$buk2 });

print "@A\n@B\n@C";
__END__
C:\test>junk
Benchmark:
running ari, buk, buk2, each for at least 1 CPU seconds
...
       ari:  1 wallclock secs ( 1.07 usr +  0.00 sys =  1.07 CPU) @ 12
+52.80/s (n=1343)
       buk:  1 wallclock secs ( 1.16 usr +  0.00 sys =  1.16 CPU) @ 23
+12.39/s (n=2687)
      buk2:  1 wallclock secs ( 1.09 usr +  0.00 sys =  1.09 CPU) @ 24
+62.88/s (n=2687)

       Rate  ari  buk buk2
ari  1253/s   -- -46% -49%
buk  2312/s  85%   --  -6%
buk2 2463/s  97%   7%   --
1 2 3 4 10 5 11 20 6 12 21 7 13 22 8 14 23 9 15 24 16 25 17 18 19
1 2 3 4 10 5 11 20 6 12 21 7 13 22 8 14 23 9 15 24 16 25 17 18 19
1 2 3 10 4 11 5 20 12 6 21 13 7 22 14 8 23 15 9 24 16 25 17 18 19

C:\test>perl58 junk.pl
       Rate  ari  buk buk2
ari   744/s   -- -41% -43%
buk  1265/s  70%   --  -3%
buk2 1307/s  76%   3%   --
11 21 7 17 2 22 1 18 23 16 13 25 6 3 9 12 20 14 15 8 4 24 19 10 5
11 21 7 17 2 22 1 18 23 16 13 25 6 3 9 12 20 14 15 8 4 24 19 10 5
11 21 7 17 2 22 1 18 23 16 13 25 6 3 9 12 20 15 14 8 4 24 19 10 5
[download]

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Even more surprising from my point of view is how much slower 5.8 is compared 5.6.1?

Examine what is said, not who speaks.
1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible
3) Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke.