my @list = qw( foo bar baz );
my %hash;
$hash{$_}++ for @list;

# now do a lookup
if ( $hash{$look_this_up} ) {
    # blah
}

use Data::Dumper;
print Dumper \%hash

__DATA__
$VAR1 = {
          'foo' => '1',
          'baz' => '1',
          'bar' => '1'
        };