sub parse {
    if ( $_[0] and $_[0] eq __PACKAGE__ or ref $_[0] eq __PACKAGE__ ) {
        shift;
    }
    my %opts;
    if ( ! @_ || scalar @_ % 2 ) {
        Bio::Phylo::Exceptions::OddHash->throw(
            error => 'Odd number of elements in hash assignment'
        );
    }
    eval { %opts = @_; };
    if ( $@ ) {
        Bio::Phylo::Exceptions::OddHash->throw( error => $@ );
    }
    if ( ! $opts{'-format'} ) {
        Bio::Phylo::Exceptions::BadArgs->throw(
            error => 'no format specified.'
        );
    }
    if ( ! grep ucfirst $opts{'-format'}, @parsers ) {
        Bio::Phylo::Exceptions::BadFormat->throw(
            error => 'no parser available for specified format.'
        );
    }
    if ( ! $opts{'-file'} && ! $opts{'-string'} ) {
        Bio::Phylo::Exceptions::BadArgs->throw(
            error => 'no parseable data source specified.'
        );
    }
    my $lib = 'Bio::Phylo::Parsers::' . ucfirst $opts{-format};
    eval "require $lib";
    if ( $@ ) {
        Bio::Phylo::Exceptions::ExtensionError->throw( error => $@ );
    }
    my $parser = $lib->_new;
    if ( $opts{-file} && $parser->can('_from_handle') ) {
        eval { open FH, '<', $opts{-file}; };
        if ( $! ) {
            Bio::Phylo::Exceptions::FileError->throw( error => $! );
        }
        $opts{-handle} = *FH;
        return $parser->_from_handle(%opts);
    }
    elsif ( $opts{-string} && $parser->can('_from_string') ) {
        return $parser->_from_string(%opts);
    }
    elsif ( $opts{-string} && ! $parser->can('_from_string') ) {
        Bio::Phylo::Exceptions::BadArgs->throw(
            error => "$opts{-format} parser can't handle strings"
        );
    }
}