Variables, Misc

Array of arrays

• A array of arrays is essentially an array of references to arrays (and should be treated as such)
  
• The same applies to an array of hashes, a hash of arrays, and a hash of hashes

Variable prefixes

$    # scalar, or an element of an array or hash
@    # array
%    # hash

Special variables

Default variable

$_   # used in many cases where no variable is explicitly stated

Command-line arguments

@ARGV      # command-line arguments for the script; 0-based
$#ARGV     # index number of the last argument
$ARGV[0]   # the first command-line argument
{$0}       # name of the program being executed

Subroutine arguments

@_      # the arguments for the subroutine; 0-based
$_[0]   # the first argument for the subroutine

my ($arg1, $arg2) = @_;

Environment variables

%ENV

Variable scope

my

• Defines a local variable within a subroutine or a source file
• Usage of my is almost always preferable to using local
• If the variable is declared outside any subroutine, it has file scope

my $scalar1 = 2;

our

• Declares a package variable
  

our $var1;