my @arr = (1,2,3,4,5,6);
my @tmp;
foreach (@arr) {
   push @tmp, ($_ > 2) ? munge($_) : $_;
}
@arr = @tmp;
print @arr;   # 1 2 3 x y z 5 x y z

sub munge {
   ($_[0] % 2) ? $_[0] : ("x","y","z");
}