当我遍历数组时,如何也获得元素的索引?

my @index_containing_o = grep { $list[$_] =~ /o/ } 0..$#list;  # ==> (0,1,3)

my %hash_of_containing_o = map { $list[$_]=~/o/?($list[$_]=>$_):() } 0..$#list
            # ==> ( 'one' => 0, 'two' => 1, 'four' => 3 )

看一看 List::MoreUtils

use List::MoreUtils qw(first_index indexes);

my $index_of_matching_element = first_index { /o/ } @list;

my @matching_indices = indexes { /o/ } @list;
my @matching_values = @list[@matching_indices];

或者只是:

my @matching_values = grep { /o/ } @list;

这将用所需内容填充2个数组,并在输入数组中循环一次:

use strict;
use warnings;
my @list = qw(one two three four five);
my @containing_o;
my @indexes_o;
for (0 .. $#list) {
    if ($list[$_] =~ /o/) {
        push @containing_o, $list[$_];
        push @indexes_o   , $_;
    }
}