my $esearch = new Clair::Bio::EUtils::ESearch( 
        term => "asthma[mh] OR hay fever[mh]",
        retmax => "100"
    );

    my $idlistref = $esearch->{IdList};
    foreach my $id (@$idlistref) {
        print "$id\n";
    }

    my $esearch = new Clair::Bio::EUtils::ESearch(
        [key => value]
    );
Performs a search given a hash of the key value pairs described on the 
ESearch website. The tool, email, and retmode parameters are set by the
module and cannot be overridden.
Once a successful search has been completed, the results are available as
key/value pairs in the Clair::Bio::EUtils::ESearch object. These are
    IdList
    A list of the IDs returned by ESearch.
    Count
    The total number of items returned.
    RetMax
    The maximum number specified in the query.
    RetStart
    The starting index specified in the query.
    QueryKey, WebEnv
    See the EUtils documentation on how to use these variables.

    my $self = shift;
    if (defined $self->{_esearch_args}) {
        return %{ $self->{_esearch_args} };
    } else {
        return undef;
    }

    my $class =shift;
    my $self = {};
    my %params = @_;
    my %esearch_args = (
        db => "PubMed",
        usehistory => "y",
    );

    # Merge with the defaults
    foreach my $key (keys %params) {
        $esearch_args{$key} = $params{$key};
    }

    # Set the required parameters
    $esearch_args{tool} = $TOOL;
    $esearch_args{email} = $EMAIL;
    $esearch_args{retmode} = "xml";

    $self->{_esearch_args} =\% esearch_args;

    my $url = build_url( base => $ESEARCH_URL, args =>\% esearch_args );

    my $handler = new Clair::Bio::EUtils::ESearchHandler;
    my $parser = new XML::Parser::PerlSAX( Handler => $handler );
    eval {
        $parser->parse(get($url));
    };
    croak "Couldn't parse ESearch results: $@" if $@;

    # Copy the results from the handler
    foreach my $key (keys %$handler) {
        $self->{$key} = $handler->{$key};
    }

    return bless($self, $class);