What are the differences between $, @, % in Perl v

问题:

This question already has answers here:

What is the difference between `$this`, `@that`, and `%those` in Perl? (5 answers)

Closed 6 years ago.

Example:

my $some_variable;
my @some_variable;
my %some_variable;

I know, @ seems to be for array, $ for primitive, is it totally right? What is % for?

回答1:

One of the nice things about Perl is that it comes with a built in manual. Type in the following command:

perldoc perlintro

and take a look at the section Perl variable types. You can also see this on line with the perldoc.perl.org section on Perl variables.

A quick overview:

• $foo is a scalar variable. It can hold a single value which can be a string, numeric, etc.
• @foo is an array. Arrays can hold multiple values. You can access these values using an index. For example $foo[0] is the first element of the array and $foo[1] is the second element of the array, etc. (Arrays usually start with zero).

• %foo is a hash, this is like an array because it can hold more than one value, but hashes are keyed arrays. For example, I have a password hash called %password. This is keyed by the user name and the values are the user's password. For example:

  $password{Fred} = "swordfish"; $password{Betty} = "secret";

  $user = "Fred"; print "The Password for user $user is $password{$user}\n"; #Prints out Swordfish $user = "Betty"; print "The Password for user $user is $password{$user}\n"; #Prints out secret

Note that when you refer to a single value in a hash or array, you use the dollar sign. It's a little confusing for beginners.

I would recommend that you get the Llama Book. The Llama Book is Learning Perl and is an excellent introduction to the language.

回答2:

$ is for scalars, @ is for arrays, and % is for hashes. See the Variable Types section of the the docs for more information.

回答3:

$ is scalar, @ is array, and % is hash.

回答4:

$var denotes a single-valued scalar variable
@var denotes an array
%var denotes an associative array or hash (they are both the same)