FAQ 4.40 What is the difference between $array[1] and @array[1]?
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From: PerlFAQ Server on 14 Jun 2010 18:00 This is an excerpt from the latest version perlfaq4.pod, which comes with the standard Perl distribution. These postings aim to reduce the number of repeated questions as well as allow the community to review and update the answers. The latest version of the complete perlfaq is at http://faq.perl.org . -------------------------------------------------------------------- 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. -------------------------------------------------------------------- The perlfaq-workers, a group of volunteers, maintain the perlfaq. They are not necessarily experts in every domain where Perl might show up, so please include as much information as possible and relevant in any corrections. The perlfaq-workers also don't have access to every operating system or platform, so please include relevant details for corrections to examples that do not work on particular platforms. Working code is greatly appreciated. If you'd like to help maintain the perlfaq, see the details in perlfaq.pod. |