foreach (@myarray) {
      $myhash{$_} = 1;
}

##</code><code>##

$myhash{$_}++ for @myarray;

##</code><code>##

if ($myhash{'blah'}) {
    do_something();
}

##</code><code>##

if (exists($myhash{'blah'})) { 
  # Do something here
}