Question

What does this function do?

    sub MyDigit {
       return <<END;
       0030\t0039
       END
    }

Answer 1

That’s called a “here-document”, and is used for breaking strings up over multiple lines as an alternative to concatenation or list operations:

print "this is ",
    "one line when printed, ",
    "because print takes multiple ",
    "arguments and prints them all!\n";
print "however, you can also " .
    "concatenate strings together " .
    "and print them all as one string.\n";

print <<DOC;
But if you have a lot of text to print,
you can use a "here document" and create
a literal string that runs until the
delimiter that was declared with <<.
DOC
print "..and now we're back to regular code.\n";

You can read more about here-documents in the manual: see perldoc perlop.