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References
I'm happiest writing Perl code that does not use references because they always give me a mild headache. Here's the short version of how they work. The backslash operator (\) computes a reference to something. The reference is a scalar that points to the original thing. The '$' dereferences to access the original thing.
Suppose there is a string...
$str = "hello"; ## original string
And there is a reference that points to that string...
$ref = \$str; ## compute $ref that points to $str
The expression to access $str is $$ref. Essentially, the alphabetic part of the variable, 'str', is replaced with the dereference expression '$ref'...
print "$$ref\n"; ## prints "hello" -- identical to "$str\n";
Here's an example of the same principle with a reference to an array...
@a = (1, 2, 3); ## original array
$aRef = \@a; ## reference to the array
print "a: @a\n"; ## prints "a: 1 2 3"
print "a: @$aRef\n"; ## exactly the same
Curly braces { } can be added in code and in strings to help clarify the stack of @, $, ...
print "a: @{$aRef}\n"; ## use { } for clarity
Here's how you put references to arrays in another array to make it look two dimensional...
@a = (1, 2, 3);
@b = (4, 5, 6);
@root = (\@a, \@b);
print "a: @a\n"; ## a: (1 2 3)
print "a: @{$root[0]}\n"; ## a: (1 2 3)
print "b: @{$root[1]}\n"; ## b: (4 5 6)
scalar(@root) ## root len == 2
scalar(@{$root[0]}) ## a len: == 3
For arrays of arrays, the [ ] operations can stack together so the syntax is more C like...
$root[1][0] ## this is 4
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