Whenever you can use the name of a variable, you can use a block that evaluates to a reference instead. For example, the following are valid syntax for specifying an array: 

@NAME    # If you have the name      e.g. @array
@BLOCK   # If you have a reference   e.g. @{ $ref }

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This is the "circumfix syntax" illustrated in the table below.

An alternative syntax colloquially known as the "arrow notation" is easier to read, but requires Perl 5.20+ in some cases. This is the "postfix syntax" illustrated in the table below.

Direct Using References
Circumfix Syntax[1] Postfix Syntax
scalar itself $s ${$sr} $sr->$*[3]
array itself @a @{$ar} $ar->@*[3]
element $a[0] ${$ar}[0] $ar->[0]
slice @a[0,1,2] @{$ar}[0,1,2] $ar->@[0,1,2][3]
index-value slice[2] %a[0,1,2] %{$ar}[0,1,2] $ar->%[0,1,2][3]
last index $#a $#{$ar} $ar->$#*[3]
hash itself %h %{$hr} $hr->%*[3]
element $h{'a'} ${$hr}{'a'} $hr->{'a'}
slice @h{'a','b','c'} @{$hr}{'a','b','c'} $hr->@{'a','b','c'}[3]
key-value slice[2] %h{'a','b','c'} %{$hr}{'a','b','c'} $hr->%{'a','b','c'}[3]
code call func(@args)
call (ignored prototype) &func(@args) &{$cr}(@args) $cr->(@args)
call (inherited @_) &func &{$cr} $cr->&*[3]
glob itself *glob *{$gr} $gr->**[3]
slot *glob{ARRAY} *{$gr}{ARRAY} $gr->*{ARRAY}[3]

  1. The curly brackets around $sr, $ar, $hr, $cr and $gr are optional when the contents of the curlies is simply a scalar.
  2. Requires Perl 5.20+.
  3. Requires Perl 5.24+. Available in Perl 5.20+ by adding both use feature qw( postderef ); and no warnings qw( experimental::postderef );, or by adding use experimental qw( postderef );. This is safe because the then-experimental feature was accepted into Perl without change.

See also:

In reply to Mini-Tutorial: Dereferencing Syntax by ikegami

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