use strict;
use warnings;

my $word = "alighthousa";
my $found;

if (($found = ( keys %{{map { $_ => 1 } ($word =~ m/([aeiou])/g) }} )) == 5) {
    print "Found all 5 vowels\n";
} else {
    print "Found only $found vowels\n";
}

##</code><code>##

($word =~ m/([aeiou])/g)
   # returns a list of all vowels found in $word

map { $_ => 1 } ($word =~ m/([aeiou])/g)
   # builds a list for initializing a hash

{ map { $_ => 1 } ($word =~ m/([aeiou])/g) }
   # a reference to an anonymous hash initialized with the list

keys %{ { map { $_ => 1 } ($word =~ m/([aeiou])/g) } }
   # return keys of the dereferenced anonymous hash
   # the keys in a hash are unique, this effectively
   # eliminates duplicates, and gives a list of unique
   # vowels found in the string

$found = ( keys ... )
   # this assigns the number of unique vowels found into $found