Del libro Modern Perl:

The given construct is a feature new to Perl 5.10. It assigns the value of an expression to the topic variable and introduces a block:
  given ($name) {
Unlike for, it does not iterate over an aggregate. It evaluates its value in scalar context, and always assigns to the topic variable:
  given (my $username = find_user())
given also makes the topic variable lexical to prevent accidental modification:

lhp@nereida:~/Lperl/src/perltesting$ cat -n 
     1  #!/usr/bin/env perl
     2  use Modern::Perl;
     4  given ('mouse') {
     5    say; 
     6    mouse_to_man( $_ ); 
     7    say;
     8  }
    10  sub mouse_to_man {
    11    $_ = shift; 
    12    s/mouse/man/;
    13    say "Inside mouse_to_man: $_";
    14  }
lhp@nereida:~/Lperl/src/perltesting$ ./ 
Inside mouse_to_man: man
given is most useful when combined with when. given topicalizes a value within a block so that multiple when statements can match the topic against expressions using smart-match semantics.

Casiano Rodríguez León
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Principios de Programación Imperativa, Funcional y Orientada a Objetos Una Introducción en Perl/Una Introducción a Perl
por Casiano Rodríguez León is licensed under a Creative Commons Reconocimiento 3.0 Unported License.

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