Perl ABC

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delete function - delete hash key

You can use the delete function to delete hash key. The value corresponding to the key is also deleted. The return value is the value that corresponds to the deleted key.

my $value = delete $hash{$key};

To use the delete function for hash reference, write:

my $value = delete $hash->{$key};

This is an example to delete the key named age using the delete function.

# Removed the key age
my %person = (name =>'Ken', age => 19);
delete $person{age};

This is an example for a hash reference.

# Delete the key. For reference.
my $person = {name =>'Ken', age => 19};
delete $person->{age};

Example program

You can see the output with an example that removes the hash key.

use strict;
use warnings;
use Data::Dumper;

# Student math scores
my %math_scores = (
  Aiko => 89,
  Kenta => 0,
  Taro => undef
);

# 1: Initial state
print "1: Initial state\n";
if (exists $math_scores{Aiko}) {
  print "\$math_scores{Aiko} exists.\n";
}
print Data::Dumper->Dump([\%math_scores], ['*math_scores']);
print "\n\n";

# Delete the key with delete
delete $math_scores{Aiko};

# 2: Deleted by delete
print "2: Deleted by delete\n";
if (exists $math_scores{Aiko}) {
  print "\$math_scores{Aiko} exists.\n";
}
else {
  print "\$math_scores{Aiko} does not exist.\n";
}

print Dumper \%math_scores;
print "\n";

Output

1: Initial state
$math_scores{Aiko} exists.
%math_scores = (
                 'Aiko' => 89,
                 'Kenta' => 0,
                 'Taro' => undef
               );


2: Deleted by delete
$math_scores{Aiko} does not exist.
%math_scores = (
                 'Kenta' => 0,
                 'Taro' => undef
               );