sub UNIVERSAL::which_constants {
  my($class, @constants) = @_;

  return grep exists $constant::declared{"$class\::$_"}, @constants;
}

use constant FOO => "a string";
use constant BAR => [ qw/ an array / ];
use constant BAZ => { qw/ a hash / };

print "constant exists - $_\n"
  for main->which_constants( qw/ ichi FOO bar BAZ one DEUX / );

__output__

constant exists - FOO
constant exists - BAZ