#! perl -slw
use strict;

our $SIZE ||= 1_000_000;

# Don't build the test array by assigning a list 
# cos that doubles the memory consumption which
# then serves to conseal the extra consumed by the grep

my @array;
push @array, $_ for 1 .. $SIZE;

printf 'Check ram before ripple'; <STDIN>;

#@array = grep not ($_ % 2), @array;

my( $s, $d );
for( $s = $d = 0; $s < @array; $d++, $s++ ) { 
 	$array[ $s ] %2 and $s++, $array[ $d ] = $array[ $s ]; 
}; 
$#array = --$d;

printf 'Check ram after ripple'; <STDIN>;

die 'M_S: Mismatch:', scalar @array, " @array[ 0, -1 ]"
	unless @array == $SIZE / 2 and "@array[ 0, -1 ]" eq "2 $SIZE";

__END__
P:\test>371457-mem
Check ram before grep 21844 kb
Check ram after grep  35856 kb

P:\test>371457-mem
Check ram before ripple 21,844 kb
Check ram after ripple  21,860 kb