Re^3: Replacing values in an array

[muba]

You can consider a hash to be much like an array, except instead of numerical indexes to access individual elements, you use strings as keys.

# Define an array:
my @basket = qw(apple banana cherry);

# Get an element from the array:
# (remember that indexes are 0-based)
print "The second kind of fruit in the basket is $basket[1]\n";

# Change an element:
$basket[1] = "date";
print "Now it is $basket[1]\n";

The above example shouldn't be unfamiliar. Now, instead of keeping a @basket that tells us what kinds of fruit we have in the basket, let's keep a %basket that can also tell us how much of that kind of fruit we have.

# Define the hash:
my %basket = (
    apple    => 12,
    banana   =>  6,
    cherry  =>  32,   # This final comma is optional,
);                    # but makes it easier to add more lines in the f
+uture.

# Get an element from the basket:
print "There are $basket{cherry} cherries in the basket.\n";

# Modify elements:
$basket{cherry}--;
print "Now there are $basket{cherry}.\n";

$basket{banana} *= 2;
print "Double Banana Bonus! $basket{banana} bananas in the basket!\n";

$basket{apple} = 10;

# Add an element:
$basket{date} = 16;


# Get all keys in the hash:
print "Fruits in my basket: ", join(", ", sort keys %basket), "\n";

# Using a variable as a key:
for my $fruit (sort keys %basket) {
    print "You want a(n) $fruit? I have $basket{$fruit} in my basket.\
+n";
}

# The 'each' function:
while (my ($fruit, $amount) = each %basket) {
    print "There are $amount ${fruit}s in my basket.\n";
}

# Getting rid of an element:
delete $basket{apple};
print "Fruits in my basket: ", join(", ", sort keys %basket), "\n";

That pretty much covers the basics of hashes. Nothing to be afraid of, and quite a useful data type!