use Benchmark;
@arr=('file.html')x1024;
timethese( -3, {
    'Slice' => '%x=();@x{@arr}=(1)x@arr',
    'For' => '%x=();for(@arr){$x{$_}=1}',
    'Map' => '%x=map{$_=>1}@arr'
} );
__END__
Benchmark: running For, Map, Slice, each for at least 3 CPU seconds...
   For: 3 secs (3.13 usr + 0.00 sys = 3.13 CPU) @ 707.72/s (n=2218)
   Map: 3 secs (3.14 usr + 0.00 sys = 3.14 CPU) @ 96.98/s (n=305)
 Slice: 4 secs (3.14 usr + 0.00 sys = 3.14 CPU) @ 1074.72/s (n=3380)