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

Training, Open Source Computer Languages

Perl •

PHP •

Python •

Tcl •

Ruby •

Lua •
- Learning to Program in Lua
- Lua Programming

C & C++ •

SQL •
- SQL - Programming and Admin

Tomcat •

Linux

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
  [3927] First match or all matches? Perl Regular Expressions - (2012-11-19)
  [3707] Converting codons via Amino Acids to Proteins in Perl - (2012-04-25)
  [3650] Possessive Regular Expression Matching - Perl, Objective C and some other languages - (2012-03-12)
  [3630] Serialsing and unserialising data for storage and transfer in Perl - (2012-02-28)
  [3411] Single and double quotes strings in Perl - what is the difference? - (2011-08-30)
  [3332] DNA to Amino Acid - a sample Perl script - (2011-06-24)
  [3322] How much has Perl (and other languages) changed? - (2011-06-10)
  [3100] Looking ahead and behind in Regular Expressions - double matching - (2010-12-23)
  [3059] Object Orientation in an hour and other Perl Lectures - (2010-11-18)
  [2993] Arrays v Lists - what is the difference, why use one or the other - (2010-10-10)
  [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)

571d

Back to
Finding all matches to a pattern in Perl regular expressions

Previous and next
or
Horse's mouth home

Forward to
Using Perl to generate multiple reports from a HUGE file, efficiently

Some other Articles

Provide a useable train service, and people will use it!
Well House Manor - perhaps the best hotel rooms in Melksham
Dark mornings, dog update, and Python and Lua courses before Christmas
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
Looking for hotel rooms in Melksham over Christmas? We still have some availability
Some different pictures from Melksham
What order are operations performed in, in a Perl expression?
I loves Melksham

4106 posts, page by page

Link to page ... 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83 at 50 posts per page

This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).

You can Add a comment or ranking to this page

Public Training Courses

Running regularly at our UK training Centre.
[Schedule] - [About] - [Book]

Like this? ??