sub first (&@) {
  my $cref = shift;
  $cref->($_) and return $_ for @_;
}

##</code><code>##

# get the first number found over 1000
$first_match = first { $_ > 1000 } @numbers;

##</code><code>##

my %seen;
@seen{@array} = ();

##</code><code>##

if (exists $seen{blah}) { ... }