With questions like these, perhaps the most general answer is...
Learning Perl

readily available (USD 30, +//-) from vendors who include the publisher, O'Reilly, and such esteemed booksellers as Amazon, Walmart, and -- very likely -- your local independent bookstore.

Update/afterthought: your OP refers to the symbol pair 'questionmark''underscore'... and so do your further responses when Monks offering help plainly refer to the pair 'dollarsign''underscore'... which is not at all the same thing.
Does your local keyboard omit the "$" sign?

In reply to Re^7: The $_ Special Variable by ww
in thread The $_ Special Variable by chuloon

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