#! perl -slw
use strict;
use Benchmark qw[ cmpthese ];


our $I //= -1;
our $N //= 4;
my @ls =  map int( 2+rand 10 ), 1 .. $N;
our $str = pack 'S*', @ls;
$str .= 'x' x ($_-1) . ' ' for @ls;

cmpthese $I, {
    a => q[
# line 1 "a"
        my $templ = "S$N" . join( ' ', map{
            "\@0 x[S$_] S \@0" .
            "S$_ x[S${ \( $N-$_ )}]" .
            '/x' x $_ .
            '/a'
        } 0 .. $N-1 );
        my( @d ) = unpack $templ, $str;
        shift @d for 1 .. $N;
        $I == 1 and print 'a ', join '|', @d;
    ],
    b => q[
# line 1 "b"
        my @l = unpack "S$N", $str;
        my $templ = "x[S$N]" . join( ' a', '', @l );
        my @d = unpack $templ, $str;
        $I == 1 and print 'b ', join '|', @d;
    ],
};

__END__
C:\test>junk -I=-1 -N=1
      Rate    a    b
a 128551/s   -- -59%
b 312873/s 143%   --

C:\test>junk -I=-1 -N=10
     Rate    a    b
a 19086/s   -- -67%
b 57153/s 199%   --

C:\test>junk -I=-1 -N=100
    Rate    a    b
a  894/s   -- -89%
b 7979/s 793%   --