使用带括号和只有一个变量的 my [英] Using my with parentheses and only one variable

问题描述

我有时会看到这样的 Perl 代码:

I sometimes see Perl code like this:

my ( $variable ) = blah....

在单个变量周围加上括号有什么意义?我认为括号只在声明多个变量时使用，例如:

What is the point of putting parentheses around a single variable? I thought parentheses were only used when declaring multiple variables, like:

my ( $var1, $var2, $var3 ) = blah...

推荐答案

出现差异时有几种情况:

There are several scenarios when there is a difference:

1. 当 array 在右侧时

my @array = ('a', 'b', 'c');
my  $variable  = @array;           #  3   size of @array
my ($variable) = @array;           # 'a'  $array[0]

当列表在右侧时

my  $variable  = qw/ a b c d /;    # 'd'  last  item of the list
my ($variable) = qw/ a b c d /;    # 'a'  first item of the list

带有变量(数组/标量)返回值的子程序

sub myFunction {
  ...
  return (wantarray() ? @array : $scalar);
}
my  $variable  = myFunction(...);  # $scalar   from the subroutine
my ($variable) = myFunction(...);  # $array[0] from the subroutine

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