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when

Perl 5 version 14.2 documentation
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when

Perl functions A-Z | Perl functions by category | The 'perlfunc' manpage
  • when EXPR BLOCK

  • when BLOCK

    when is analogous to the case keyword in other languages. Used with a foreach loop or the experimental given block, when can be used in Perl to implement switch /case like statements. Available as a statement after Perl 5.10 and as a statement modifier after 5.14. Here are three examples:

    1.     use v5.10;
    2.     foreach (@fruits) {
    3.         when (/apples?/) {
    4.             say "I like apples."
    5.         }
    6.         when (/oranges?/) {
    7.             say "I don't like oranges."
    8.         }
    9.         default {
    10.             say "I don't like anything"
    11.         }
    12.     }
    14.     # require 5.14 for when as statement modifier
    15.     use v5.14;
    16.     foreach (@fruits) {
    17. 	say "I like apples." 	    when /apples?/; 
    18. 	say "I don't like oranges." when /oranges?;
    19.                 default { say "I don't like anything" }
    20.         }
    22.         use v5.10;
    23.         given ($fruit) {
    24.                 when (/apples?/) {
    25.                         say "I like apples."
    26.                 }
    27.                 when (/oranges?/) {
    28.                         say "I don't like oranges."
    29.                 }
    30.                 default {
    31.                         say "I don't like anything"
    32.                 }
    33.         }

    See Switch statements in perlsyn for detailed information.