Package Pattern Basics

Use a package as the namespace for related behavior.
package-pattern Packages group related routines under a stable name.
                            name
                            name = "Perl" (default)name = "Mira"name = "Ada"
                        

                            package_pattern_basics.pl
                        
Replay: real traced execution (multi-file project)

                            use strict;
use warnings;

package Greeter;

sub label {
    my ($name) = @_;
    return "hello:$name";
}

package main;

my $name = "Perl";
my $message = Greeter::label($name);

print "name=$name\n";
print "message=$message\n";
use strict;
use warnings;

package Greeter;

sub label {
    my ($name) = @_;
    return "hello:$name";
}

package main;

my $name = "Mira";
my $message = Greeter::label($name);

print "name=$name\n";
print "message=$message\n";
use strict;
use warnings;

package Greeter;

sub label {
    my ($name) = @_;
    return "hello:$name";
}

package main;

my $name = "Ada";
my $message = Greeter::label($name);

print "name=$name\n";
print "message=$message\n";

                        
1$name ← Perl⋯13my $name→ Perl = "Perl"; #@name="Mira", "Ada"14my $message = Greeter::label($namePerl);⋯
2$name ← Perl⋯6sub label {7    my ($name→ Perl) = @_;8    return "hello:$namePerl";9}⋯
3$message ← hello:Perl⋯13my $name = "Perl"; #@name="Mira", "Ada"14my $message→ hello:Perl = Greeter::label($namePerl);1516print "name=$namePerl\n";17print "message=$messagehello:Perl\n";⋯outputname=Perl
message=hello:Perl
1$name ← Mira⋯13my $name→ Mira = "Mira";14my $message = Greeter::label($nameMira);⋯
2$name ← Mira⋯6sub label {7    my ($name→ Mira) = @_;8    return "hello:$nameMira";9}⋯
3$message ← hello:Mira⋯13my $name = "Mira";14my $message→ hello:Mira = Greeter::label($nameMira);1516print "name=$nameMira\n";17print "message=$messagehello:Mira\n";⋯outputname=Mira
message=hello:Mira
1$name ← Ada⋯13my $name→ Ada = "Ada";14my $message = Greeter::label($nameAda);⋯
2$name ← Ada⋯6sub label {7    my ($name→ Ada) = @_;8    return "hello:$nameAda";9}⋯
3$message ← hello:Ada⋯13my $name = "Ada";14my $message→ hello:Ada = Greeter::label($nameAda);1516print "name=$nameAda\n";17print "message=$messagehello:Ada\n";⋯outputname=Ada
message=hello:Ada