This code works:
my $href = shift @_; # get reference to hash
my %h = %{$href}; # dereference hash
This one does not:
my %h = %{shift @_};
As well as this one:
my %h = ${$_[0]}
Why?
One more time to be precisly:
1 #!/usr/bin/perl -w
2 use strict;
3 use warnings;
4
5 my %h;
6 sub a {
7
8 # that works - result 1
9 my $href = $_[0] || shift;
10 %h = %{$href};
11
12 # that does not work - result 0
13 # my %h = %{$_[0]};
14
15 # as well as that one - result 0
16 # my %h = %{shift @_};
17 $h{1}=2;
18 }
19
20 a(\%h);
21 print scalar (keys %h) . "\n";
In other words line 16 - it doesn't.
This will work.
my %h = %{shift @_};
This won't.
my %h = ${$_[0]} # not ${$_[0]}
That sigil is supposed to be %
my %h = %{$_[0]}
also, use warnings;, and use strict;
HINT: The reason your above example doesn't work, is only one example doesn't declare a lexical variable %h = %{$href}; is not my %h = %{$href};