$ ./pm_temp 
Benchmark: timing 50000 iterations of aighearach, aighearach_longrand,
+ ewijaya, ewijaya_longrand, pg, pg_longrand, scooterm, scooterm_longr
+and...
aighearach:  1 wallclock secs ( 0.88 usr +  0.00 sys =  0.88 CPU) @ 56
+818.18/s (n=50000)
aighearach_longrand:  1 wallclock secs ( 0.83 usr +  0.00 sys =  0.83 
+CPU) @ 60240.96/s (n=50000)
   ewijaya:  4 wallclock secs ( 3.70 usr +  0.00 sys =  3.70 CPU) @ 13
+513.51/s (n=50000)
ewijaya_longrand:  2 wallclock secs ( 3.22 usr +  0.00 sys =  3.22 CPU
+) @ 15527.95/s (n=50000)
        pg:  1 wallclock secs ( 0.86 usr +  0.00 sys =  0.86 CPU) @ 58
+139.53/s (n=50000)
pg_longrand:  1 wallclock secs ( 0.99 usr +  0.00 sys =  0.99 CPU) @ 5
+0505.05/s (n=50000)
  scooterm:  2 wallclock secs ( 0.95 usr +  0.01 sys =  0.96 CPU) @ 52
+083.33/s (n=50000)
scooterm_longrand:  2 wallclock secs ( 0.86 usr +  0.00 sys =  0.86 CP
+U) @ 58139.53/s (n=50000)
                       Rate ewijaya ewijaya_longrand pg_longrand scoot
+erm aighearach scooterm_longrand   pg aighearach_longrand
ewijaya             13514/s      --             -13%        -73%     -
+74%       -76%              -77% -77%                -78%
ewijaya_longrand    15528/s     15%               --        -69%     -
+70%       -73%              -73% -73%                -74%
pg_longrand         50505/s    274%             225%          --      
+-3%       -11%              -13% -13%                -16%
scooterm            52083/s    285%             235%          3%      
+ --        -8%              -10% -10%                -14%
aighearach          56818/s    320%             266%         12%      
+ 9%         --               -2%  -2%                 -6%
scooterm_longrand   58140/s    330%             274%         15%      
+12%         2%                --  -0%                 -3%
pg                  58140/s    330%             274%         15%      
+12%         2%                0%   --                 -3%
aighearach_longrand 60241/s    346%             288%         19%      
+16%         6%                4%   4%                  --
[download]

#!/usr/bin/perl -- # -*-PERL-*-
use Data::Dumper;
use Benchmark 'cmpthese';

my @data = ([1,2], [1,3], [2,3], [2,4], [3,4]);
my @data_longrand = map { [ int( rand( 25 ) ), int( rand( 25 ) ) ] } 1
+ .. 10_000;

cmpthese( 50_000,
      {  ( map { $_ => qq[$_( \@data )] } qw/ pg scooterm ewijaya aigh
+earach / ),
         ( map { $_.'_longrand' => qq[$_( \@data_longrand )] } qw/ pg 
+scooterm ewijaya aighearach / ),
      },
    );

sub pg {
    my %vertices;

    for my $i ( 0 .. $#_ ) {
        $vertices{$_[$i][$_]} = 1 for (0 .. $#{$_[$i]});
    }
    return sort keys %vertices;
}

sub scooterm {
    my  %hTemp;
    my  @aTemp = map{@{$_}} @_;
    @hTemp{@aTemp}  = ();
    return sort keys %hTemp;
}

sub aighearach {
    my ( %unique );
    for ( my $i = 0; $i < @_; $i++ ) {
        @unique{@{$_[$i]}} = undef;
    }
    return sort keys %unique;
}

sub ewijaya {
    my @edges = @_;
    my @vertices;
    my @uniqv; 

    for my $i ( 0 .. $#edges ) {
    for my $j ( 0 .. $#{$edges[$i]} ) {
        push @vertices, $edges[$i][$j];
    }
    }

    @uniqv = sort keys %{{map {$_,1} @vertices}};
    return @uniqv;
}

__END__
[download]