An explicit array is @arr = qw(a b x) and an anonymous one is $array_ref = [qw(c d e)]

Use print and/or Data::Dumper or better Data::Dump to se in action:

 my $array_ref = [qw(c d e)]; print Dumper $array_ref;

The doc covering this is perlref

> %chars hash, are you saying that a new hash is made for each word in the list, and that the keys of that hash are the individual characters in the word?

Yes! try it to see; print is your first debugging tool:

use strict;
use warnings;

my $good = [qw( allo mallo malo)];
my $bad  = [qw( tillo sillo sallo)];

foreach my $list ($good, $bad){
    print "got list [@{$list}]\n";
    my $has_unique;
    foreach my $word(@$list){
          print "analizing word [$word]\n";
          my %chars;
          foreach my $char ($word =~ /./g){
            print "\tGot char [$char]\n";
            $chars{$char}+= 1;
          }
          print "\tchars count is:\n";
          print map{"\t$_ = $chars{$_} "}keys %chars;
          print "\n";
          if (scalar keys %chars == length $word){
               print "\t$word has no repeated letters (keys of \%chars
+ are equal to the length of \$word)\n";
              $has_unique++;
          }
          print "\n";
    }
    print "I print the whole list: ",(join ' ', @$list),"\n\n" if $has
+_unique;
}

# output

got list [allo mallo malo]
analizing word [allo]
        Got char [a]
        Got char [l]
        Got char [l]
        Got char [o]
        chars count is:
        l = 2   a = 1   o = 1

analizing word [mallo]
        Got char [m]
        Got char [a]
        Got char [l]
        Got char [l]
        Got char [o]
        chars count is:
        l = 2   a = 1   m = 1   o = 1

analizing word [malo]
        Got char [m]
        Got char [a]
        Got char [l]
        Got char [o]
        chars count is:
        l = 1   a = 1   m = 1   o = 1
        malo has no repeated letters (keys of %chars are equal to the 
+length of $word)

I print the whole list: allo mallo malo

...
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