SPUG: A hash of hashes and arrays

mike mike206 at gmail.com
Mon Aug 1 08:53:09 PDT 2005

%perldoc -f ref

      ref EXPR
      ref     Returns a true value if EXPR is a reference, false
              otherwise.  If EXPR is not specified, "$_" will be
              used.  The value returned depends on the type of
              thing the reference is a reference to.  Builtin
              types include:


              If the referenced object has been blessed into a
              package, then that package name is returned
              instead.  You can think of "ref" as a "typeof"

                  if (ref($r) eq "HASH") {
                      print "r is a reference to a hash.\n";
                  unless (ref($r)) {
                      print "r is not a reference at all.\n";
                  if (UNIVERSAL::isa($r, "HASH")) {  # for subclassing
                      print "r is a reference to something that isa hash.\n";

On 8/1/05, Duane Blanchard <dblanchard at gmail.com> wrote:
> Hi all,
> I have a hash of hashes and arrays. I'm able to print the all the keys
> of the outer hash, and print the embedded hashes and arrays
> individually, now I want to print the entire contents of the outer
> (matrix) hash.
> I need something like:
> for each key in the outer hash
> {   if (the key is a reference to a hash)
>     {    print the contents of the hash;
>     }
>     elsif (the key is a reference to an array)
>     {    print the contents of the array;
>     }
> }
> I have everything in place, but don't know how to tell whether I'm
> looking at a hash or an array.
> Any hints?
> P.S. In linguistics, we call the embedded sentences "embedded
> sentences," clever, I know, and those into which they are embedded
> "matrix sentences." What is the parlance in Perl/formal languages?
> Duane Blanchard
> There are 10 kinds of people in the world;
> those who know binary and those who don't.
> _____________________________________________________________
> Seattle Perl Users Group Mailing List
>      POST TO: spug-list at pm.org
> SUBSCRIPTION: http://mail.pm.org/mailman/listinfo/spug-list
>     MEETINGS: 3rd Tuesdays, Location: Amazon.com Pac-Med
>     WEB PAGE: http://seattleperl.org/

More information about the spug-list mailing list