my (%hash, @array);

@array = ('one', 'two', 'three');

@hash{@array} = (1) x @array;

if (exists $hash{'one'}) { .... }

##</code><code>##

use Benchmark qw(timethese);

my $iterations = 300_000;
my @array = ( "best", 1..49, "average", 51..99, "worst" );

for my $search (qw( best average worst )) {
	print "Timing '$search' case:\n";
	
	timethese($iterations, {
		'map' => sub {
			my %hash = ();
			%hash = map { $_=>1 } @array;
			if ($hash{$search}) { 1 }
		},
		'xop' => sub {
			my %hash = ();
			@hash{@array} = (1) x @array;
			if ($hash{$search}) { 1 }
		},
		'for1' => sub {
			my %hash = ();
			for (@array) { $hash{$_} = 1 }
			if ($hash{$search}) { 1 }
		},
		'for2' => sub {
			for (@array) { if ($_ eq $search) { 1; last } }
		},
		'for3' => sub {
			if (do {
				my $f=0;
				$_ eq $search and ($f=1),last for @array;
				$f
			}) { 1 }
		},
		'grep' => sub {
			if (grep $search eq $_, @array) { 1 }
		},
	});
}

__END__

Timing 'best' case:

Benchmark: timing 300000 iterations of for1, for2, for3, grep, map, xop...
      for1: 116 wallclock secs (117.60 usr +  0.00 sys = 117.60 CPU) @ 2551.02/s (n=300000)
      for2:  1 wallclock secs ( 1.21 usr +  0.00 sys =  1.21 CPU) @ 247933.88/s (n=300000)
      for3:  3 wallclock secs ( 2.36 usr +  0.00 sys =  2.36 CPU) @ 127118.64/s (n=300000)
      grep: 27 wallclock secs (26.20 usr +  0.00 sys = 26.20 CPU) @ 11450.38/s (n=300000)
       map: 236 wallclock secs (234.47 usr +  0.00 sys = 234.47 CPU) @ 1279.48/s (n=300000)
       xop: 93 wallclock secs (92.93 usr +  0.00 sys = 92.93 CPU) @ 3228.24/s (n=300000)

Timing 'average' case:

Benchmark: timing 300000 iterations of for1, for2, for3, grep, map, xop...
      for1: 111 wallclock secs (110.18 usr +  0.00 sys = 110.18 CPU) @ 2722.82/s (n=300000)
      for2: 20 wallclock secs (18.35 usr +  0.00 sys = 18.35 CPU) @ 16348.77/s (n=300000)
      for3: 20 wallclock secs (18.29 usr +  0.00 sys = 18.29 CPU) @ 16402.41/s (n=300000)
      grep: 26 wallclock secs (26.09 usr +  0.00 sys = 26.09 CPU) @ 11498.66/s (n=300000)
       map: 220 wallclock secs (219.22 usr +  0.00 sys = 219.22 CPU) @ 1368.49/s (n=300000)
       xop: 93 wallclock secs (92.83 usr +  0.00 sys = 92.83 CPU) @ 3231.71/s (n=300000)

Timing 'worst' case:

Benchmark: timing 300000 iterations of for1, for2, for3, grep, map, xop...
      for1: 109 wallclock secs (109.24 usr +  0.00 sys = 109.24 CPU) @ 2746.25/s (n=300000)
      for2: 35 wallclock secs (35.65 usr +  0.00 sys = 35.65 CPU) @ 8415.15/s (n=300000)
      for3: 34 wallclock secs (34.06 usr +  0.00 sys = 34.06 CPU) @ 8807.99/s (n=300000)
      grep: 26 wallclock secs (26.19 usr +  0.00 sys = 26.19 CPU) @ 11454.75/s (n=300000)
       map: 222 wallclock secs (222.51 usr +  0.00 sys = 222.51 CPU) @ 1348.25/s (n=300000)
       xop: 93 wallclock secs (93.05 usr +  0.00 sys = 93.05 CPU) @ 3224.07/s