You could change the while loop to something like:

my %seen;
while (my $ref = $pdbh->fetchrow_hashref()) {
    for (qw(mon tue wed thu fri sat sun)) {
       my $result = lcfirst($_).$ref->{$_} if $ref->{$_};
       if ($seen{$result}++) {
           warn "$seen found already";
       }
       else {
           push @results,$result;
       }
    }
}
print join("\n",@results);
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That should print out the results with duplicates removed in the format you seem to want.

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.
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