Question

use strict;
use warnings;

my %table = qw/schmoe joe smith john simpson bart/; 
my $da =1;
my($key, $value); # Declare two variables at once 
while ( ($key, $value) = each(%table) ) 
{ 
    $table{$key} = ++$da;
} 

print %table;

the output:

schmoe2smith3simpson4

I was expecting to get to 2345...

What is wrong with my foreach?

Answer 1

I think you misunderstood something.

The values are changed, but when you code print %table;, you print keys and values.

With Data::Dumper module, it’s more clear :

$ Perl
Perl Console 0.4
Perl> use Data::Dumper
Perl> my %table = qw/schmoe joe smith john simpson bart/; 
6

Perl> my $da =1;
1

Perl> my($key, $value);
2

Perl> while ( ($key, $value) = each(%table) ) { $table{$key} = ++$da; }
0

Perl> print Dumper \%table
$VAR1 = {
          'schmoe' => 2,
          'smith' => 3,
          'simpson' => 4
        };
1

Perl> print %table;
schmoe2smith3simpson41

If you want to iterate through the hash, you can do :

while(my($key, $value) = each %table) {
    print "$key=$value\n";
}

but the hash name is confusing, it’s not a table but a hash.

Another solution to iterate through the hash :

foreach my $key (keys %table) {
    print "$key=$table{$key}\n";
}