Why aren't the outputs of the two print statements same. I want
to reconstruct %hash1 into %hash2.
========================================
use strict;
use Data:
umper;
my %hash1 = (key1 => 'value1', 'key2' => 'value2');
my %hash2 = eval Dumper(%hash1);
print Dumper(%hash1);
print Dumper(%hash2);
========================================
I am trying to save the Dumper output to the database and later trying
to get the same data structure.
You're making several mistakes with the usage of Data:
umper.
1) Dumper() takes a list of structures to dump. You are passing it a
list of values (using a hash in a list context). If you want to dump
just the single variable %hash1, you have to pass a reference to that
hash:
print Dumper(\%hash1);
2) Dumper() returns a string that starts with "$VAR1 = ". If you are
trying to eval() that string, you are trying to execute code
containing the variable $VAR1. When you use strict, you need to pre-
declare all your variables. You are eval'ing code without checking
for an error. If you had checked the value of $@, you'd see that the
eval failed because $VAR1 was not previously declared.
3) Because the string that Dumper() returns represents code that
assigns to a reference, if you eval that code, you are getting a
reference out of it. You need to dereference that reference.
There are several solutions to your problem:
(1) Predeclare $VAR1
$ perl -le'
use strict;
use Data:
umper;
my %hash1 = (key1 => "value1", key2 => "value2");
my $VAR1;
my %hash2 = %{ eval Dumper(\%hash1) };
print Dumper(\%hash1);
print Dumper(\%hash2);
'
$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
(2) Use the Dump() method rather than the Dumper() function, which
lets you set the name you wish to use for the dumped variables:
$ perl -le'
use strict;
use Data:
umper;
my %hash1 = (key1 => "value1", key2 => "value2");
my $hash2;
eval Data:
umper->Dump([\%hash1], ["hash2"]);
print Dumper(\%hash1);
print Dumper($hash2);
'
$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
(3) use the Storable module instead, which has (imho) a nicer
interface for this sort of thing, and is also a core module.
$ perl -le'
use strict;
use Storable qw/freeze thaw/;
my %hash1 = (key1 => "value1", key2 => "value2");
my %hash2 = %{ thaw(freeze(\%hash1)) };
use Data:
umper;
print Dumper(\%hash1, \%hash2);
'
$VAR1 = {
'key2' => 'value2',
'key1' => 'value1'
};
$VAR2 = {
'key2' => 'value2',
'key1' => 'value1'
};
Hope that helps,
Paul Lalli
