in reply to main package

What package does it belong to ?

If you declared it as a package variable, whichever package statement is in effect. In your code, that would be "main".

If you declared it as a lexical variable, it's not found in a package.

What is main package ?

The currently selected package when the interpreter starts.

If I declare $var in a program, does it automatically belong to main package ?

No, the package in effect.

if I use strict, is it required to use main before the $anything ($main::anything) ?

If you declared it as a package variable, no.

If you declared it as a lexical variable, yes. Otherwise, you'll be accessing the lexical variable.

How does $anything become a part of main package ?

I don't understand.

Or does main mean main body (and not subroutines) of program that we are dealing with ?

It's just a namespace into which variables and subs can be placed. It doesn't mean anything.

So does it mean that everything from "#!/usr/bin/perl" to the "print $var; " excluding subroutines is main ?

Absent an overriding package statement, all code (including subroutines) will be compiled into main. That means that package variables and subs will be placed in the main namespace by default.

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Re^2: main package
by manishrathi (Beadle) on Oct 06, 2009 at 18:39 UTC
    "If you declared it as a package variable"

    So if I declare a variable without "my" , is that a package variable ? If I declare a variable in the sub routine without "my" , is it still a package variable ?

    "whichever package statement is in effect"

    How to know which opackage statement is in effect ? From the comment , it appears that default is main package. If I want to use same variable name in another program, how can I do that ?
[reply]

      You should always declare variables with either our or my.

      "whichever package statement is in effect".Here's how you set the package.

      use strict;
use warnings;

# the default namespace is main
# so this is a variable in main.
our $movie='Chitty Chitty Bang Bang';

# set the current package
package A::B::C;

# We've changed the package - it is no longer main
# now its A::B::C

# if a variable is undefined in the current package,
# then Perl looks for a variable in main of the same name
# these two statements are the same and do not cause
# warnings

print "movie=$movie\n";
print "movie=$main::movie\n";

# but once we declare the variable in A::B::C, an
# unqualified name is presumed to be in the current 
# package

# declare a package variable in the namespace A::B::C
our $movie = 'Mary Poppins';

# these print different things
print "movie=$movie\n";       # prints Marry Poppins
print "movie=$main::movie\n"; # prints Chitty Chitty Bang Bang

{
   # this overrides the current package. The override
   # will last until the next matching curly brace
   package NotA::NotB;

   # this is $movie but in the NotA::NotB namespace
   # its a different variable from either $main::movie
   # or $A::B::C::movie

   my $movie = 'Pippi Longstocking';
   
   print "movie=$movie\n";          #prints Pippi Longstocking
   print "movie=$A::B::C::movie\n"; #prints Mary Poppins
   print "movie=$main::movie\n";    #prints Chitty Chitty Bang Bang

# } matches { enclosing package statement
# so this ends the code block where NotA::NotB is the
# package.
}

# now we are back to A::B::C being the current package 
print "movie=$movie\n";       # prints Marry Poppins
print "movie=$main::movie\n"; # prints Chitty Chitty Bang Bang

      [download]

      Hope that helps.

      Best, beth

[reply]
[d/l]

      So if I declare a variable without "my" , is that a package variable ?

      There are three ways to declare a variable.

      my $var; declares a lexical var.
      our $var; declares a package var. The declaration is lexical.
      use vars qw( $var ); declares a package var. The declaration is global.

      If I declare a variable in the sub routine without "my" , is it still a package variable ?

      It's irrelevant whether a sub is being compiled or not.

      How to know which package statement is in effect ?

      Look for a package statement in the source, or call __PACKAGE__.

      If I want to use same variable name in another program, how can I do that ?

      The question makes no sense. Please clarify

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