use strict; use warnings;

my @to_be_searched = qw/ lots of elements /;
my @to_find = qw/ fewer elements /;

my %lookup = map { $_ => 1 } @to_be_searched;

for my $element ( @to_find ) {
    if ( exists $to_be_searched{ $element } ) {
        # do something
    } else {
        # do other thing
    }
}