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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";

__END__

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

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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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