What about tie?
#!/usr/bin/perl
{
package AssignOnce;
use strict;
use warnings;
use Carp ();
use Tie::Hash;
use parent -norequire => 'Tie::StdHash'; # why, oh why, is Tie::St
+dHash hidden in Tie::Hash?
sub STORE
{
my ($self,$key,$value)=@_;
if (exists $self->{$key}) {
Carp::carp("Overwriting hash key '$key', old value: '$self
+->{$key}', new value: '$value'");
}
$self->SUPER::STORE($key,$value);
}
}
use strict;
use warnings;
use Data::Dumper;
our %h;
tie %h,'AssignOnce';
%h=(
one => 1,
two => 2,
one => 3,
);
print Dumper(\%h);
Result:
Overwriting hash key 'one', old value: '1', new value: '3' at tie.pl l
+ine 29
$VAR1 = {
'one' => 3,
'two' => 2
};
Alexander
--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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