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map { $code .= "\$hash{$_} = 1;\n" } @array; eval "$code";

use Benchmark;

...
        eval "$code";
        }
});

Benchmark: timing 10000 iterations of btrott, plaid...
    btrott:  1 wallclock secs ( 0.56 usr +  0.00 sys =  0.56 CPU)
     plaid: 23 wallclock secs (22.07 usr +  0.06 sys = 22.13 CPU)