Hi,i have a code fragment below.

%tag = (); #line 1
  $tag{'info'} = $datastring; #line 2
  $resp = $ua->request(  #$ua is a user agent
       POST 'http://10.2.3.0' ,
       Content_Type  => application/x-www-form-urlencoded
       Content       => [ %tag ] #line 3

correct
correct
the hash is being assigned. hash consists of keys and values. both keys and values would be assigned to Content.

Strictly speaking, I think what is being assigned is a reference to an array, the elements of which are the keys and values of the hash %tag (which are the string 'info' and the value of the variable $datastring)

I will be inclined to say that if you have some basic knowledge Perl, you will understand the syntax used on those 3 lines. But they alone do not make much sense in my opinion. It's actually what the code does that is more important.

So are you working on a program using HTTP::Request? If so, please take a look at the POD for the module. It will tell you what methods are provided, and the arguments you need to use. Then, you simply provide the arguments as needed.