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The difference between dot (a.k.a. full stop, period) and comma in Perl

If (Perl) I write
  $x = "12";
  $y = "25";
  print $x,$y;
  print $x.$y;
  print "\n";

Then I'll get output
  12251225

In other words - the output is the same. So is there a difference?

Yes - there's a huge difference.

$x.$y - using the dot operator - joins the two strings together (concatenates them) into one.

$x,$y - using the comma - passes the two strings forward as a list so they are printed one after another.

You can see the difference if you write
  @abc = sort($y,$x);
  @def = sort($y.$x);


In the first case, using , (comma), @abc is a list that's two sorted elements long, so it's
  ['12','25']
whereas in the second case, using . (full stop / period), @def is a list of one item, nothing to sort, so it's
  ['2512']

Full example, including output, [here] from this week's Perl Programming Training Course.

(written 2011-12-09, updated 2011-12-17)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
P212 - Perl - More on Character Strings
  [4452] Binary data handling - Python and Perl - (2015-03-09)
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  [2877] Further more advanced Perl examples - (2010-07-19)
  [2874] Unpacking a Perl string into a list - (2010-07-16)
  [2834] Teaching examples in Perl - third and final part - (2010-06-27)
  [2801] Binary data handling with unpack in Perl - (2010-06-10)
  [2657] Want to do a big batch edit? Nothing beats Perl! - (2010-03-01)
  [2379] Making variables persistant, pretending a database is a variable and other Perl tricks - (2009-08-27)
  [2230] Running a piece of code is like drinking a pint of beer - (2009-06-11)
  [1947] Perl substitute - the e modifier - (2008-12-16)
  [1735] Finding words and work boundaries (MySQL, Perl, PHP) - (2008-08-03)
  [1727] Equality and looks like tests - Perl - (2008-07-29)
  [1510] Handling Binary data (.gif file example) in Perl - (2008-01-17)
  [1336] Ignore case in Regular Expression - (2007-09-08)
  [1305] Regular expressions made easy - building from components - (2007-08-16)
  [1251] Substitute operator / modifiers in Perl - (2007-06-28)
  [1230] Commenting a Perl Regular Expression - (2007-06-12)
  [1222] Perl, the substitute operator s - (2007-06-08)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [928] C++ and Perl - why did they do it THAT way? - (2006-11-16)
  [737] Coloured text in a terminal from Perl - (2006-05-29)
  [608] Don't expose your regular expressions - (2006-02-15)
  [597] Storing a regular expression in a perl variable - (2006-02-09)
  [586] Perl Regular Expressions - finding the position and length of the match - (2006-02-02)
  [583] Remember to process blank lines - (2006-01-31)
  [453] Commenting Perl regular expressions - (2005-09-30)


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Using Perl to generate multiple reports from a HUGE file, efficiently
The difference between dot (a.k.a. full stop, period) and comma in Perl
Finding all matches to a pattern in Perl regular expressions
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