All scarlar variables

• start with the "$" symbol and a letter
• + other letters, numbers or underscore.
• The contents can contain 1 to many characters, numbers or other special characters.
• Upper vs lower case letters represent different variable names. $Valueand $value represent two different variables.

You can assign the contents to a scalar variable by...

$x = "value";
$x = "can contain a phrase";
$x = <STDIN>;
# takes input from keyboard

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Special values must be proceeding by a backslash (\) in order to be include with in the contents of scalar variable. The following table is a list of such values.

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All array variables

• start with an "@"
• Contain a "list" or "elements"
• Each element is a separate 'scalar' variable.

You can assign the contents to a array by...

@x = ("value1", "value2", "many words")

You can refer to each element of the array variable individual by using the "$" scalar symbol and an element number in '[ ]'s.

value of $x[0] is 'value1'
value of $x[1] is 'value 2'
value of $x[2] is 'many words'

$x[4] = "new entry";
# sets the 4th element to 'new entry'

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To get the length of all elements in an array, let a scalar
variable = array variable. @name = ("roger", "petersen");

$namesize = @name;
# value of $namesize = 14
($namesize) = @name;
# value of $namesize = 'roger'.
# Set to first element in the array      

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To determine the number of elements in an array use  '$#'

@x = ("value1", "value2", "many words");
$numelements = $#x;
# $numelements = 2, remember count starts at 0

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push and pop are used to add or subtract elements from the right side of an array.

@x = (1, 2, 3);
push(@x, "4");
# adds new element '4'.  @x = 1, 2, 3, 4
$last = pop(@x);
# $last =4, @x = 1, 2, 3

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unshift and shift are used to add or subtract elements from the left side.

@x = (4, 5, 6);
unshift(@x, 1,2,3);
# @x = 1,2,3,4,5,6
$firstvalue = shift(@x);
# $firstvalue = 1,  @x = 2,3,4,5,6

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reverse is used to reverse the order of all elements in an array.

@x = (1, 2, 3, 4, 5);
@x = reverse(@x);  # @x = 5,4,3,2,1

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sort is used to return the sorted values of all elements

@x = (1, 2, 4, 8, 16, 32, 64);
@x = sort(@x); # @x = 1,16, 2, 32,4, 68, 8

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All hash variables

• start with the '%' symbol.
• Hash variables are similar to arrays with the extra feature of having a 'reference key'.

You assign the contents to a hash variable in pairs...

%mydata=("key1","value1","key2","value2","key3","data associated with key3")

Just like arrays, each key and associated data element can be referenced by using scalar variables. The key value is enclosed with '{  }'.

$key="key1";
$data = $mydata{$key1};
#$data now contains 'value1'
$data =$mydata{"key3"};
#$data now contains 'data associated with key3'

Another method for assignment is...

$zipcode("60126") = "Elmhurst, IL";
# creates key 'of 60126' with a value of 'Elmhurst, IL'
print $zipcode{"60126"};
# prints the value for the key, i.e. 'Elmhurst, IL'

$var(123) = "456.7"
# creates a key of '123' with a value of '456.7'
$var(123} += 3;
# increase the value of key '123' by 3, i.e. value = '459.7'

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The keys function only returns all of the keys for a hashed variable. The values function only returns all of values for a hased variable.

$zipcode("60126") = "Elmhurst, IL";
$zipcode("60016") = "Des Plaines, IL";
@zips = keys(%zipcode);
# @zips contains 60126, 60016
@cities = values(%zipcode);
# @cities contains 'Elmhurst, IL' and 'Des Plaines, IL'      

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The each function is used to access all elements of the entire hash in pairs.

while (($zip, $city) = each(%zipcode)) {
    print "The city for zip code $zip is $city\n";
}

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The delete function is used to delete a specified key and value of a has variable.

delete $zipcode{"60126"};
# deletes the key 60126 and the value 'Elmhurst, IL'    

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