When I say that "I'm taking the dogs for a walk", I don't literally carry the dogs for a walk - they walk themselves and I just hold the leads.

Statement of the obvious? Yes!

But you would be surprised how many programmers pass complete full data structures into named blocks of code - "subroutines" - rather than just passing the address / a refernce to the data structure which is rather like the dog's lead. Th etemptation to pass data in this inefficient way is particularly stong in Perl where
  domysub(@info);
passes a complete second copy of the data in the list in @info to the sub, whereas
  domysub(\@info);
would simply pass in a reference - lightweight, like the dog leads - even though the dogs shadowed here weigh 31kgs and 36kgs.

Our Perl Courses go into this subject in a much more through way - not only do we teach you Perl, but we teach you to write good Perl. Next course - 6 weeks time ... places still available!

(written 2012-10-28, updated 2012-11-03)

 Z203 - Cat and Dog
  [62] Technical Open House - (2004-09-25)
  [96] Variable Scope - (2004-10-22)
  [547] Taking the dog for a walk - (2005-12-29)
  [744] We can offer a room, but we can't operate on a dog - (2006-06-05)
  [771] From cat breeder to Cobol to Perl - (2006-06-21)
  [2029] Also for the eyes of the cat - (2009-02-07)
  [2132] Learning about Lurchers - (2009-04-18)
  [2138] Ski bore ... train bore ... dog bore - (2009-04-24)
  [2140] Beware - giving copyright away when you upload a picture - Dogs Trust - (2009-04-25)
  [2167] Watching the tele - (2009-05-10)
  [2252] Leaping dog, Leaping horse, copyright of old masters - (2009-06-20)
  [2271] Dogs Trust, Dog Show, Newbury - (2009-07-06)
  [2295] The dog is not in trouble - (2009-07-17)
  [2450] Family Gathering at 404, The Spa - (2009-10-11)
  [2451] Gypsy says - (2009-10-12)
  [2456] Bright Eyes - (2009-10-16)
  [2496] A better design of mouth - (2009-11-07)
  [2499] ourdog is Greyhound, Staffie and Ginger Cake - (2009-11-09)
  [2555] Bookkeeping - (2009-12-29)
  [2689] Can my dog eat potatoes? Doggie Dietary Research, and political sleaze! - (2010-03-23)
  [2787] Sleeping in on Sunday - (2010-05-30)
  [2897] The Land of the Black Labrador - (2010-08-01)
  [3096] Contrast in pictures - (2010-12-20)
  [3324] Rabbit Shelter - (2011-06-12)
  [3338] Return trip - Dogs Trust, Newbury - (2011-06-27)
  [3530] A typical weekend?? - (2011-11-28)
  [3533] No message - just doggy pictures of the new doggy - (2011-11-30)
  [3537] Letting the foster parents know ... too little or too much? - (2011-12-04)
  [3541] I loves Melksham - (2011-12-06)
  [3553] Changes to morning routines - (2011-12-16)
  [3561] Happy Christmas ... a Christmas morning walk in Melksham - (2011-12-25)
  [3606] Gypsy and Billy enjoy the snow - (2012-02-10)
  [3625] An update on Billy the Greyhound and Gypsy the Lurcher - (2012-02-25)
  [3674] Off to walk the dogs - (2012-03-30)
  [3675] Spring 2012 - (2012-03-30)
  [3737] Postcards from Barmouth - (2012-05-20)
  [3908] Black dogs at Halloween - (2012-10-31)
  [3920] Challenge for a photographer - (2012-11-10)
  [3936] Lisa is home today ... - (2012-11-26)
  [3943] With us for a year already! - (2012-12-03)
  [4016] Red, yellow, green or pink dog? Yellow Dog Project - (2013-02-23)
  [4130] Soft furnishings up a Welsh Mountain - (2013-07-03)
  [4180] Exceptionally, I sign a petition - on a life and death issue for Irish dogs - (2013-09-20)
  [4189] Who are we - Lisa, Graham, Gypsy and Billy - (2013-10-07)
  [4316] Too many Staffies, too many lurchers - (2014-11-16)
  [4333] Misty Melksham Morning - (2014-11-30)
  [4417] Crisp morning, fast run - (2015-02-06)
  [4433] Different views of a Welsh Valley - but headed home - (2015-02-20)
  [4507] In favour of adoption rather than puppy purchase - dogs! - (2015-06-07)
  [4517] Black dog day - and Bobby still seeks his new home - (2015-09-26)
  [4526] Day trip to Lancaster - (2015-10-10)
  [4666] Spring at Well House Manor - (2016-03-27)

P217 - Perl - More than Simple Lists and Hashes!
  [43] Hash of lists in Perl - (2004-09-09)
  [293] Course follow-ups - (2005-04-27)
  [1514] Autovivification - the magic appearance of variables in Perl - (2008-01-21)
  [2241] Perl references - $$var and \$var notations - (2009-06-15)
  [2840] Just pass a pointer - do not duplicate the data - (2010-06-30)
  [2877] Further more advanced Perl examples - (2010-07-19)
  [2996] Copying - duplicating data, or just adding a name? Perl and Python compared - (2010-10-12)
  [3007] Setting up a matrix of data (2D array) for processing in your program - (2010-10-21)
  [3072] Finding elements common to many lists / arrays - (2010-11-26)
  [3105] Adventure with references to lists and lists of references - (2010-12-26)
  [3118] Arrays of arrays - or 2D arrays. How to program tables. - (2011-01-02)
  [3399] From fish, loaves and apples to money, plastic cards and BACS (Perl references explained) - (2011-08-20)
  [3406] Not multidimentional arrays - but lists of lists. Much more flexible. Perl! - (2011-08-26)
  [3444] Take the dog on a lead - do not carry her. Perl references. - (2011-09-17)
  [3577] How to do multidimensional arrays (or rather lists and hashes) in Perl - (2012-01-14)

P208 - Perl - Lists
  [28] Perl for breakfast - (2004-08-25)
  [140] Comparison Chart for Perl programmers - list functions - (2004-12-04)
  [230] Course sizes - beware of marketing statistics - (2005-02-27)
  [240] Conventional restraints removed - (2005-03-09)
  [355] Context in Perl - (2005-06-22)
  [463] Splitting the difference - (2005-10-13)
  [560] The fencepost problem - (2006-01-10)
  [622] Queues and barrel rolls in Perl - (2006-02-24)
  [762] Huge data files - what happened earlier? - (2006-06-15)
  [773] Breaking bread - (2006-06-22)
  [928] C++ and Perl - why did they do it THAT way? - (2006-11-16)
  [968] Perl - a list or a hash? - (2006-12-06)
  [1304] Last elements in a Perl or Python list - (2007-08-16)
  [1316] Filtering and altering Perl lists with grep and map - (2007-08-23)
  [1703] Perl ... adding to a list - end, middle, start - (2008-07-09)
  [1828] Perl - map to process every member of a list (array) - (2008-10-09)
  [1917] Out of memory during array extend - Perl - (2008-12-02)
  [1918] Perl Socket Programming Examples - (2008-12-02)
  [2067] Perl - lists do so much more than arrays - (2009-03-05)
  [2226] Revision / Summary of lists - Perl - (2009-06-10)
  [2484] Finding text and what surrounds it - contextual grep - (2009-10-30)
  [2813] Iterating over a Perl list and changing all items - (2010-06-15)
  [2833] Fresh Perl Teaching Examples - part 2 of 3 - (2010-06-27)
  [3400] $ is atomic and % and @ are molecular - Perl - (2011-08-20)
  [3548] Dark mornings, dog update, and Python and Lua courses before Christmas - (2011-12-10)
  [3669] Stepping through a list (or an array) in reverse order - (2012-03-23)
  [3870] Writing more maintainable Perl - naming fields from your data records - (2012-09-25)
  [3939] Lots of ways of doing the same thing in Perl - list iteration - (2012-12-03)
  [4609] Mapping an array / list without a loop - how to do it in Perl 6 - (2016-01-03)

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