in reply to hard versus soft reference to ARRAY's

ok : i should have used strict en warnings 
use strict;
use warnings;

my $dwarfs = [ qw(Doc Grumpy Happy Sleepy Sneezy Dopey Bashful) ];

print "@{$dwarfs}\n";
my @removed=();
my $removed="";

@removed = splice @{$dwarfs},3 ,2;
#$removed =  [ @removed ]; #1. please notice : this makes a copy first
+ of @removed . # changes to @{$removed} will NOT affect @removed
# OUTPUT : Sleepy Sneezy
$removed = \@removed ;   #2. please notice : this is a hard reference 
+. # changes to @{$removed} will affect @removed.
# OUTPUT : Sleepy 
# let's examine the above : Just uncomment  one of the above beginning
+ with : $removed
pop @{$removed} ;
print "@removed\n";

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Re^2: hard versus soft reference to ARRAY's
by AnomalousMonk (Archbishop) on Jan 25, 2016 at 23:40 UTC

    This is, for the most part, just a picky restatement of some points I was trying to make above. But references are tricky, so I want to make these points clearly.

    The statement
        $removed = [ @removed ];
    creates a hard reference to an anonymous array initialized by a shallow copy from the  @removed array. The statement
        $removed = \@removed;
    also creates a hard reference, but to the named  @removed array. The nature of both these references is the same, but their referents, the things they reference, are different. Hence, the difference in behavior when using these two references.

    #$removed =  [ @removed ]; #1. please notice : this makes a copy first of @removed . # changes to @{$removed} will NOT affect @removed

    It is not true that changes to  $removed will not affect the referent. Because the anonymous array is initialized by a shallow copy, accesses by reference to lower levels of the referent, if such exist, can change the referent. E.g.: 

    c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(dd);
 ;;
 my @ra = ([ qw(fee fie foe) ], [ qw(original stuff) ], [ qw(uno dos t
+res) ]);
 dd \@ra;
 ;;
 my $hardref = [ @ra ];
 dd $hardref;
 print '-------------';
 ;;
 $hardref->[1] = 'ZOT!';
 $hardref->[0][2] = 'KAPOW!';
 $hardref->[2][1] = 'WHAM!';
 dd $hardref;
 dd \@ra;
"
[
  ["fee", "fie", "foe"],
  ["original", "stuff"],
  ["uno", "dos", "tres"],
]

[
  ["fee", "fie", "foe"],
  ["original", "stuff"],
  ["uno", "dos", "tres"],
]

-------------
[["fee", "fie", "KAPOW!"], "ZOT!", ["uno", "WHAM!", "tres"]]

[
  ["fee", "fie", "KAPOW!"],
  ["original", "stuff"],
  ["uno", "WHAM!", "tres"],
]

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    Note that a change to the "top" level of the  $hardref reference ('ZOT!') does not change the original content of the  @ra array, but a more indirect or "lower" level access ('KAPOW!' 'WHAM!') does. As I say, tricky.

    Give a man a fish:  <%-{-{-{-<

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