A third way,

{
    my $remap = { qw(
                  THIS THAT
                  BLACK WHITE
                  TALL SHORT   
                  ) };

    sub remap_closure {
        exists $remap->{ $_[0] } ?
            $remap->{ $_[0] }    :
            undef;
    }
}
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By checking for existence, the hash does not keep growing new undefined keys as possibles are tried. That is not a problem with the others since each invocation gets a new hash with them.

After Compline,
Zaxo