#!/usr/bin/perl -w
use strict;

my @prime= qw( 1 2 3 5 7 11 13 17 19 23 29 31
    37 41 43 47 53 59 61 67 71 73 79 83 89 97 );
my %prime; @prime{@prime}= (1)x@prime;

sub one {
    my $av= [ 0..100 ];

    my $o= 0;
    for my $i (  0..$#$av  ) {
        if(  $prime{$i}  ) {
            $av->[$o++]= $av->[$i];
        }
    }
    $#$av= $o-1;
    return $av;
}

sub for {
    my $av= [ 0..100 ];

    for my $i ( reverse 0 .. $#$av ) {
        splice( @$av, $i, 1 )
            if  ! $prime{$i};
    }

    return $av;
}

sub whl {
    my $av= [ 0..100 ];

    my $i= @$av;
    while(  0 <= --$i  ) {
        splice( @$av, $i, 1 )
            if  ! $prime{$i};
    }

    return $av;
}

printf "(%s)\n", join " ", @{&one()};
printf "(%s)\n", join " ", @{&for()};
printf "(%s)\n", join " ", @{&whl()};

use Benchmark qw( cmpthese );
cmpthese( -3, {
    one => \&one,
    for => \&for,
    whl => \&whl,
} );
__END__
       Rate  whl  for  one
whl  2610/s   -- -63% -78%
for  7049/s 170%   -- -41%
one 11986/s 359%  70%   --
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