#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my @list = qw{one two three four one};
my %lookup;
for my $i (0..$#list){
  push @{$lookup{$list[$i]}}, $i;
}

print "@{$lookup{one}}\n";

#print Dumper \%lookup;
[download]

my @where = grep { $question[$_] eq $search } 0 .. $#question;
[download]

Using a hash for lookup is a not so dead simple adaptation, but still feasible. In the meantime, wfsp has shown how it can be done.