I don't think there is a need for extra data structures for this, just use the @do_not_want in a loop and skip those keys from %hash that match one of them: 
my %hash = (
        ytd => 1.5,
        mtd => 2.0,
        wtd => 2.5,
        Jumbo_Tron => "United Center",
        Meat_Pie => "Gross",
        "Word" => "Association",
        );
my @do_not_want = qw{ ytd mtd wtd };

foreach my $k (keys %hash) {
        next if scalar grep { m/$k/ } @do_not_want;
        print "$k => $hash{$k}\n";
}

[download]
Which would output the following. You just replace the print line with whatever operatiosn you need to perform on the "wanted" keys of %hash. 
Meat_Pie => Gross
Jumbo_Tron => United Center
Word => Association

[download]

---
echo S 1 [ Y V U | perl -ane 'print reverse map { $_ = chr(ord($_)-1) } @F;'

In reply to Re: Selecting a Specific Keys in Relation to a List by tuxz0r
in thread Selecting a Specific Keys in Relation to a List by awohld

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