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lists / context demo
Subroutines in Perl example from a Well House Consultants training course
More on Subroutines in Perl [link]

This example is described in the following article(s):
   • Seven new intermediate Perl examples - [link]

Source code: l2 Module: P209

=head1 Lists and Context

* If you use an @abc, you mean the WHOLE of a list
* If you use $abc[10], you mean a scalar member of a list
* If you use $#abc, you mean the top index number of a list

* If you refer to a list IN A LIST CONTEXT you mean all elements
* In a SCALAR context, you mean the NUMBER OF ELEMNST in the list
* In a DOUBLE QUOTE context, you mean a string of all element ...
  ... linked with a space between each of them

# A list - starts with an @
@wentto = ("Lacock","Calne","Cherhill","Avebury");

# HOWEVER - members are scalars, so start with a $
print "First place was $wentto[0]\n";

# Refer to a list but in a scalar context
# means the LENGTH of the list!
$nplace = @wentto;
print "We went to $nplace places\n";

# List starts at zero, so last element is
# numbered one LESS THAT the number of elements
print "Our last stop was $wentto[$nplace-1]\n";

# As an alternative, $# returns LAST POSITION
print "Our last stop was $wentto[$#wentto]\n";

# Or ... you can count down from the top
print "Our last stop was $wentto[-1]\n";

# List or scalar context - with or without spaces
print "All the places ",@wentto,"\n";
print "All the places @wentto\n";
# In a scalar context - NUMBER of elements
print "Count the places: ",@wentto+0,"\n";

$places = join(", ",@wentto);
$places =~ s/(.*),/\1 and/;
print $places,"\n";


Dorothy:p82 grahamellis$ perl l2
First place was Lacock
We went to 4 places
Our last stop was Avebury
Our last stop was Avebury
Our last stop was Avebury
All the places LacockCalneCherhillAvebury
All the places Lacock Calne Cherhill Avebury
Count the places: 4
Lacock, Calne, Cherhill and Avebury
Dorothy:p82 grahamellis$

Learn about this subject
This module and example are covered on the following public courses:
 * Perl Programming
 * Perl bootcamp
 * Learning to program in Perl
 * Perl Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Perl are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Subroutines in Perl" training module. You'll find a description of the topic and some other closely related examples on the "Subroutines in Perl" module index page.

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