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Perl functions such as chop change their input parameters

Typically, functions / named blocks of code take a series of operands / parameters as inputs, and return a result which is saved into another variable - here's an example in Perl:

  $size = length($persname);

Incoming value - read from $persname
Action defined in - length
Outgoing value - saved into $size

However - I have said typically, as in some languages it's possible for a function to amend the input values as well. Take a look at this Perl line:

  $boots = chop($feet);

$boots gets set to the final character of the incoming string in $feet which is modified by the removal of that character. So:

Incoming in $feet: Hello[cr]
Outgoing in $boots: [cr]
Outgoing in $feet: Hello

Once you're aware of this action from the chop function, it works very well for you ... but it comes as a bit of a surprise the first time you see it!

Complete source example (and sample output) [here]. We cover this subject (and of course a lot more!) on our Perl Programming course.

(written 2012-01-10, updated 2012-01-14)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
P202 - Perl Fundamentals
  [4324] Learning to program - variables and constants - (2014-11-22)
  [3917] BODMAS - the order a computer evaluates arithmetic expressions - (2012-11-09)
  [3542] What order are operations performed in, in a Perl expression? - (2011-12-07)
  [3398] Perl - making best use of the flexibility, but also using good coding standards - (2011-08-19)
  [3329] Perl from basics - (2011-06-20)
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  [2442] Variable storage - Perl, Tcl and Python compared - (2009-10-08)
  [1946] Variable Types in Perl - (2008-12-15)
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  [1726] Hot Courses - Perl - (2008-07-28)
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  [1312] Some one line Perl tips and techniques - (2007-08-21)
  [748] Getting rid of variables after you have finished with them - (2006-06-06)
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P209 - Subroutines in Perl
  [3833] Learning to use existing classes in Perl - (2012-08-10)
  [3066] Separating groups of variables into namespaces - (2010-11-24)
  [2929] Passing a variable number of parameters in to a function / method - (2010-08-20)
  [2833] Fresh Perl Teaching Examples - part 2 of 3 - (2010-06-27)
  [2550] Do not copy and paste code - there are much better ways - (2009-12-26)
  [2069] Efficient calls to subs in Perl - avoid duplication, gain speed - (2009-03-07)
  [1921] Romeo and Julie - (2008-12-04)
  [1860] Seven new intermediate Perl examples - (2008-10-30)
  [1850] Daisy the Cow and a Pint of Ginger Beer - (2008-10-21)
  [1784] Global - Tcl, PHP, Python - (2008-09-03)
  [1782] Calling procs in Tcl and how it compares to Perl - (2008-09-02)
  [1202] Returning multiple values from a function (Perl, PHP, Python) - (2007-05-24)
  [1163] A better alternative to cutting and pasting code - (2007-04-26)
  [969] Perl - $_ and @_ - (2006-12-07)
  [775] Do not duplicate your code - (2006-06-23)
  [588] Changing @INC - where Perl loads its modules - (2006-02-02)
  [531] Packages in packages in Perl - (2005-12-16)
  [357] Where do Perl modules load from - (2005-06-24)
  [308] Call by name v call by value - (2005-05-11)
  [96] Variable Scope - (2004-10-22)


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Multiple buttons calling the same proc in wish (tcl/tk)
Perl functions such as chop change their input parameters
New in Java 7 - and why we are not running public Java 7 courses
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