What is the difference between `$this`, `@that`, and `%those` in Perl?

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A useful mnemonic for Perl sigils are:

  • $calar
  • @rray
  • %ash

Matt Trout wrote a great comment on blog.fogus.me about Perl sigils which I think is useful so have pasted below:

Actually, perl sigils don’t denote variable type – they denote conjugation – $ is ‘the’, @ is
‘these’, % is ‘map of’ or so – variable type is denoted via [] or {}. You can see this with:

my $foo = 'foo';
my @foo = ('zero', 'one', 'two');
my $second_foo = $foo[1];
my @first_and_third_foos = @foo[0,2];
my %foo = (key1 => 'value1', key2 => 'value2', key3 => 'value3');
my $key2_foo = $foo{key2};
my ($key1_foo, $key3_foo) = @foo{'key1','key3'};

so looking at the sigil when skimming perl code tells you what you’re going to -get- rather
than what you’re operating on, pretty much.

This is, admittedly, really confusing until you get used to it, but once you -are- used to it
it can be an extremely useful tool for absorbing information while skimming code.

You’re still perfectly entitled to hate it, of course, but it’s an interesting concept and I
figure you might prefer to hate what’s -actually- going on rather than what you thought was
going on 🙂

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