Perl Dereferencing Notation

Perl Dereferencing Notation and Arrays of Arrays

Imagine that each row of @N represents information about some important object.
Every innermost letter represents a scalar. All other letters are names of arrays.

Relationships so far:

@L is $N[0]
  @C is $L[0]          @C is $N[0][0]
    $A is $C[0]          $A is $N[0][0][0]
    $B is $C[1]          $B is $N[0][0][1]
  @J is $L[1]          @J is $N[0][1]
    @F is $J[0]          @F is $N[0][1][0]
      $D is $F[0]          $D is $N[0][1][0][1]
      $E is $F[1]          $E is $N[0][1][0][2]
    @I is $J[1]          @I (is $N[0][1][1]
      $G is $I[0]          $G is $N[0][1][1][0]
      $H is $I[1]          $H is $N[0][1][1][1]
  $K is $L[2]          $K is $N[0][2]

@M is $N[1]

Arrays can be stored as references (scalars) and retrieved (converted
back from references to normal arrays).

Storing arrays as references

To store an array as a reference, precede its name by \ :

# add scalars to @C
push @C, $A;
push @C, $B;

# add scalars to @F
push @F, $D;
push @F, $E;

# add scalars to @I
push @I, $G;
push @I, $H;

# add arrays F and I as references to @J
push @J, \@F;
push @J, \@I;

# add array C and J as references to @L; add K
push @L, \@C;
push @L, \@J;
push @L, $K;

# add array L as a reference to @N
push @N, \@L;

# with proper buildup, array M could be added to @N
push @M, \@L;

Retrieving values from a arrays of references

Dereference notation:

To dereference an array reference (to turn a reference into an array), add @{ before it and add } after it.
```
$ref    # reference
@{$ref} # array made from reference
```
To refer to cell $i of a dereferenced array reference, replace the @ at the start with $ and add [$i] at the end.
```
@{$ref}    # array made from reference
${$ref}[5] # element 5 of the array
```
A pattern starting with ${$ and ending with [x]}[y] can be reduced to $ and [x][y]
```
${$N[0]}[0]       reduces to $N[0][0]
${${$N[0]}[0]}[0] reduces to $N[0][0][0]
```

Dereference notation for the example

Item $i in @N is $N[$i]
Item 0 in @N is $N[0]
  The array in $N[0] is @{$N[0]}
  Therefore @L is @{$N[0]}
  Item $j in @L is $L[$j]           or ${$N[0]}[$j]  or $N[0][$j]
  Item 0 in @L is $L[0]             or ${$N[0]}[0]   or $N[0][0]
    The array in $L[0] is @{$L[0]}  or @{${$N[0]}[0]}  or @{$N[0][0]}
    Therefore @C is @{$L[0]}        or @{${$N[0]}[0]}  or @{$N[0][0]}
    Item 0 in @C is $C[0]           or ${${$N[0]}[0]}[0]  or $N[0][0][0]
    Therefore $A is $C[0]           or ${${$N[0]}[0]}[0]  or $N[0][0][0]
    Item 1 in @C is $C[1]           or ${${$N[0]}[0]}[1]  or $N[0][0][1]
    Therefore $B is $C[1]           or ${${$N[0]}[0]}[1]  or $N[0][0][1]
  Item 1 in @L is $L[1]                 or ${$N[0]}[1]  or $N[0][1]
    The array in $L[1] is @{$L[1]}      or @{${$N[0]}[1]}  or @{$N[0][1]}
    Therefore @J is @{$L[1]}            or @{${$N[0]}[1]}  or @{$N[0][1]}
    Item 0 in @J is $J[0]               or ${${$N[0]}[1]}[0]  or $N[0][1][0]
      The array in $J[0] is @{$J[0]}    or ${${$N[0]}[1]}[0]  or $N[0][1][0]
      Therefore @F is @{$J[0]}          or @{${${$N[0]}[1]}[0]}  or @{$N[0][1][0]}
      Item 0 in @F is $F[0]             or ${${${$N[0]}[1]}[0]}[0]  or $N[0][1][0][0]
        The array in $F[0] is @{$F[0]}  or @{${${${$N[0]}[1]}[0]}[0]}  or @{$N[0][1][0][0]}
        Therefore @D is @{$F[0]}        or @{${${${$N[0]}[1]}[0]}[0]}  or @{$N[0][1][0][0]}
      Item 1 in @F is $F[1]             or ${${${$N[0]}[1]}[0]}[1]  or $N[0][1][0][1]
        The array in $F[1] is @{$F[1]}  or @{${${${$N[0]}[1]}[0]}[1]}  or @{$N[0][1][0][1]}
        Therefore @E is @{$F[1]}        or @{${${${$N[0]}[1]}[0]}[1]}  or @{$N[0][1][0][1]}
    Item 1 in @J is $J[1]               or ${${$N[0]}[1]}[1]  or $N[0][1][1]
      The array in $J[1] is @{$J[1]}    or ${${$N[0]}[1]}[1]  or $N[0][1][1]
      Therefore @I is @{$J[1]}          or @{${${$N[0]}[1]}[1]}  or @{$N[0][1][1]}
      Item 0 in @I is $I[0]             or ${${${$N[0]}[1]}[1]}[0]  or $N[0][1][1][0]
        The array in $I[0] is @{$I[0]}  or @{${${${$N[0]}[1]}[1]}[0]}  or @{$N[0][1][1][0]}
        Therefore @G is @{$I[0]}        or @{${${${$N[0]}[1]}[1]}[0]}  or @{$N[0][1][1][0]}
      Item 1 in @I is $I[1]             or ${${${$N[0]}[1]}[1]}[1]  or $N[0][1][1][1]
        The array in $I[1] is @{$I[1]}  or @{${${${$N[0]}[1]}[1]}[1]}  or @{$N[0][1][1][1]}
        Therefore @H is @{$I[1]}        or @{${${${$N[0]}[1]}[1]}[1]}  or @{$N[0][1][1][1]}
  Item 2 in @L is $L[2]             or ${$N[0]}[2]  or $N[0][2]
    Therefore $K is $L[2]           or ${$N[0]}[2]  or $N[0][2]
Item 1 in @N is $N[1]               
  The array in $N[1] is @{$N[1]}    
  Therefore @M is @{$N[1]}