Grep:
@moo = grep {($_ % 2 > 0)?0:1;} @moo;

Or easier to add more complex code if you:
@moo = grep {; {if ($_ % 2 > 0){ 0; last; } 1;}}  @moo;
# PS why do I need that first ';' - I don't know but I do

For Loop:
for (my $i=0;$i<@moo;$i++)
{ if ($moo[$i] % 2 > 0)  {splice @moo, $i, 1;} }
# wow is this slow