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Scope - our, my and local
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):
   • Some more advanced Perl examples from a recent course - [link]

Source code: scope Module: P209

# our - default - global
# my - variable is lexically scoped to the block it's declared in
# local - previous global is stored and a new one created that only exists to
# the end of the block it's declared in

# My and local differences -
# local replaces the global variable temporarily so works for special variables such as $"
# local variables are also visible within subs, by my ones are not

sub marine {
        print "The value of \$a_44r is $a_44r\n";
        print "$cherry\n$banana\n";

# Scalar - integer, float, string, reference, regex

# default global, auto typing!
# ----------------------------

$cherry = "Round and Red";
$banana = "Long and Yellow";

$a_44r = 16;

$a_44r = "The long hard road to Lochinver";

# With "my" variables is lexically scoped to next }

my $cherry = "Pip wrapped in flesh";
print "$cherry\n";
marine; # Cherry is going to be Round and Red

local $banana = "Not really a fruit more a pithstick";
print "$banana\n";
marine; # Banana is going to be the new value
marine; # Banana has been restored


my scopes variable to current block
local takes a backup copy of the variable and restores it at the end of the block

local is BAD and my is GOOD (bit simplistic, mind!)



Sample Output

wizard:pl graham$ perl scope
The value of $a_44r is 16
Round and Red
Long and Yellow
The value of $a_44r is The long hard road to Lochinver
Round and Red
Long and Yellow
Pip wrapped in flesh
The value of $a_44r is The long hard road to Lochinver
Round and Red
Long and Yellow
Not really a fruit more a pithstick
The value of $a_44r is The long hard road to Lochinver
Round and Red
Not really a fruit more a pithstick
The value of $a_44r is The long hard road to Lochinver
Round and Red
Long and Yellow
wizard:pl graham$

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.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
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• All of these resources can be searched through through our search engine
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