$WHERE = join ' OR ', map { X => $_ }, @ARRAY;
$DB->update(
   { table => 'table',
     fields => { Y => 0 },
     where => $WHERE
   } );

##</code><code>##

my @ARRAY=qw/foo bar baz/;
my @WHERE=('OR') x (2*@ARRAY - 1);
for (0 .. $#ARRAY) {
  $WHERE[2*$_] = { X => $ARRAY[$_] };
}