my %hash = ( 1 .. 100000 );

timethese( 500000, {
  'obfu'   => 'my @result;
               for my $key ( keys %hash ) {
                   $result[ @result ] = "$key:$hash{ $key }";
               }',
  'push'   => 'my @result;
               for my $key ( keys %hash ) {
                   push @result, "$key:$hash{ $key }";
               }',
});

#Results:
#Benchmark: timing 500000 iterations of obfu, push...
#      obfu:  5 wallclock secs ( 2.93 usr +  0.01 sys =  2.94 CPU) @ 169836.96/s (n=500000)
#      push:  3 wallclock secs ( 2.94 usr +  0.00 sys =  2.94 CPU) @ 170357.75/s (n=500000)