I am wanting to verify the existence of various strings within a text file, & the order of these strings is not mandated.

I have implemented a loop which looks for each successive string. However, there is no need to look for strings already encountered, so I would like to remove strings from the search list as they encountered.

splice() seemed to be the obvious choice to delete elements within the array, or so I thought. The following simplified code executed under Perl 5.8.8 doesn't seem to delete any elements within the search list:

#!/bin/env perl

use strict;

use Data::Dumper;

use constant REQUIRED_FIELDS => qw/zero one two three four five six se
+ven/;

my $a = [qw/three one two/];
print Data::Dumper->Dump([$a], ['a']);
verify($a);
exit;

sub verify {
    my $a = shift;

    my $fields = [REQUIRED_FIELDS];

    my $href = {};
    foreach my $e (@$a) {
        my $i;
        foreach my $field (@$fields) {
            if ($e eq $field) {
                $href->{$field} = 0;
                splice @$fields, $i, 0;
                print Data::Dumper->Dump([$i, $fields], [qw/i fields/]
+);
            }
            ++$i;
        }
    }

    print Data::Dumper->Dump([$href], [qw/href/]);
}
[download]

Execution yields the following output:

$ perl test.pl
$a = [
       'three',
       'one',
       'two'
     ];
$i = 3;
$fields = [
            'zero',
            'one',
            'two',
            'three',
            'four',
            'five',
            'six',
            'seven'
          ];
$i = 1;
$fields = [
            'zero',
            'one',
            'two',
            'three',
            'four',
            'five',
            'six',
            'seven'
          ];
$i = 2;
$fields = [
            'zero',
            'one',
            'two',
            'three',
            'four',
            'five',
            'six',
            'seven'
          ];
$href = {
          'three' => 0,
          'one' => 0,
          'two' => 0
        };
$
[download]

Is the array used by foreach cached? I am not understanding why splice is not pruning the found values.

Thanks!

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