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FAQ 4.40 What is the difference between $array[1] and @array[1]?

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4.40: What is the difference between $array[1] and @array[1]?

(contributed by brian d foy)

The difference is the sigil, that special character in front of the
array name. The "$" sigil means "exactly one item", while the "@" sigil
means "zero or more items". The "$" gets you a single scalar, while the
"@" gets you a list.

The confusion arises because people incorrectly assume that the sigil
denotes the variable type.

The $array[1] is a single-element access to the array. It's going to
return the item in index 1 (or undef if there is no item there). If you
intend to get exactly one element from the array, this is the form you
should use.

The @array[1] is an array slice, although it has only one index. You can
pull out multiple elements simultaneously by specifying additional
indices as a list, like @array[1,4,3,0].

Using a slice on the lefthand side of the assignment supplies list
context to the righthand side. This can lead to unexpected results. For
instance, if you want to read a single line from a filehandle, assigning
to a scalar value is fine:

$array[1] = <STDIN>;

However, in list context, the line input operator returns all of the
lines as a list. The first line goes into @array[1] and the rest of the
lines mysteriously disappear:

@array[1] = <STDIN>; # most likely not what you want

Either the "use warnings" pragma or the -w flag will warn you when you
use an array slice with a single index.


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