Example:
my $some_variable;
my @some_variable;
my %some_variable;
I know, @ seems to be for an array and $ for a primitive. Is it totally right?
What is % for?
4 Answers
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.
1 Comment
Chris Lambrou
What about a @ before a $? In the example below - $baseball_team_ids is passed to a subroutine then referenced in a new variable creation. my $total_ids = scalar(@$baseball_teamIDs);
$ is for scalars, @ is for arrays, and % is for hashes. See the Variable Types section of the documentation for more information.
1 Comment
brian d foy
Well,
$ for for single item, @ is for zero or more items, and % is for zero or more pairs. When used with an identifier (variable name) and no indexing, that translates to what you say. However, all of these are different variables: $scalar, $array[0], $hash{"key"}. And these are different variables: @array, @hash{qw(key1 key2)}, as are these: %array[0], %hash{qw(key1 key2)} (although the hash window slicing wasn't. thing when this answer was produced).$ is scalar, @ is array, and % is hash.
4 Comments
nicola
yeah, but why $_ and @_ are the same for containing pass-in parameters to a funcction? or i'm wrong?
ikegami
@nicola, Array and hash elements use "$".
$_[0] is the first element of @_. Both are unrelasted to $_.
Eric Strom
@nicola =>
@_ is an array containing all of the arguments passed to a function. $_ is a scalar containing the current item being worked with in situations like for (@array) {...}. $_ has nothing to do with @_. Where you are likely getting confused is that to access an individual element of the argument list, you would write $_[0], which accesses the first element. Here the sigil changes to $ to denote that you are accessing a scalar, however the trailing [0] tells perl that it is accessing a scalar element of the array in _ or in other words, @_.brian d foy
Well,
$ for for single item, @ is for zero or more items, and % is for zero or more pairs. When used with an identifier (variable name) and no indexing, that translates to what you say. However, all of these are different variables: $scalar, $array[0], $hash{"key"}. And these are different variables: @array, @hash{qw(key1 key2)}, as are these: %array[0], %hash{qw(key1 key2)} (although the hash window slicing wasn't. thing when this answer was produced).$var denotes a single-valued scalar variable
@var denotes an array
%var denotes an associative array or hash (they are both the same)
sigilon google.%is for hashes. Refer Here