[Bioperl-l] The usage of $field->$_

[Peng Yu]

In the Eutilities cookbook,
http://www.bioperl.org/wiki/HOWTO:EUtilities_Cookbook

I see the following code,

    print join(',', grep {$field->$_} qw(is_date
               is_singletoken is_hierarchy is_hidden is_numerical)),"\n\n";

I'm not quite familiar with the usage of $field->$_. I don't see where
it is covered in man perlvar (I don't the usage of $_ for pattern
matching, but not in $variable->$). Would you please let me know where
is the document that explain this usage?

-- 
Regards,
Peng