Perl chokes on that line because you're trying to use double-quotes inside a double-quoted string. To Perl, this is one string: "name is ${input_queue}{" and this is another string: "}\n".

Here are several different ways to do what you're trying to do:

1. Use single quotes on the hash key.
   print "name is ${input_queue}{'name'}\n";
   
2. Don't use any quotes on the hash key.
   print "name is ${input_queue}{name}\n";
   This works because the key, 'name', is a bareword. It wouldn't work with a key like 'this-is-a-key'.
   
   
3. Use a quoting operator on the string.
   print qq(name is ${input_queue}{"name"}\n);
   qq{} is just like double-quotes, but you get to choose the delimiter.
   

One last point: the braces around the hash name are optional: $input_queue{name} = "blah";. If you prefer the extra braces, that's okay too.

UPDATE: Please see tye's answer for why ${input_queue}{'name'} doesn't mean the same as $input_queue{'name'} in a double-quoted string.