Changes

==== Hashes ====

==== Hashes ====

    A hash represents a set of key/value pairs:

A hash represents a set of key/value pairs:

         my %fruit_color = ("apple", "red", "banana", "yellow");

         my %fruit_color = ("apple", "red", "banana", "yellow");

    You can use whitespace and the => operator to lay them out more nicely:

You can use whitespace and the '''=>''' operator to lay them out more nicely:

         my %fruit_color = (

         my %fruit_color = (

         );

         );

    To get at hash elements:

To get at hash elements:

         $fruit_color{"apple"}; # gives "red"

         $fruit_color{"apple"}; # gives "red"

 

You can get at lists of keys and values with '''keys()''' and '''values()'''.

    You can get at lists of keys and values with keys() and values().

         my @fruits = keys %fruit_colors;

         my @fruits = keys %fruit_colors;

         my @colors = values %fruit_colors;

         my @colors = values %fruit_colors;

    Hashes have no particular internal order, though you can sort the keys and loop through them.

Hashes have no particular internal order, though you can sort the keys and loop through them.

    Just like special scalars and arrays, there are also special hashes. The most well known of these is %ENV which contains environment variables. Read all about it (and other special variables) in perlvar.

Just like special scalars and arrays, there are also special hashes. The most well known of these is '''%ENV''' which contains environment variables. Read all about it (and other special variables) in [http://perldoc.perl.org/perlvar.html perlvar].

Scalars, arrays and hashes are documented more fully in perldata.

Scalars, arrays and hashes are documented more fully in [http://perldoc.perl.org/perldata.html perldata].

More complex data types can be constructed using references, which allow you to build lists and hashes within lists and hashes.

More complex data types can be constructed using references, which allow you to build lists and hashes within lists and hashes.

     print "Scalars begin with a $variables->{'scalar'}->{'sigil'}\n";

     print "Scalars begin with a $variables->{'scalar'}->{'sigil'}\n";

Exhaustive information on the topic of references can be found in perlreftut, perllol, perlref and perldsc.

Exhaustive information on the topic of references can be found in [http://perldoc.perl.org/perlreftut.html perlreftut], [http://perldoc.perl.org/perllol.html perllol], [http://perldoc.perl.org/perlref.html perlref] and [http://perldoc.perl.org/perldsc.html perldsc].

 

=== Variable scoping ===

=== Variable scoping ===