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Posts Tagged ‘1;

This is one of the errors that I got when I started using perl modules.
It was because I had not put “1;” at the end of my perl module. So I did not get the error after I put “1;” at the end of the perl module.

why is the “1;” necessary at the end of perl modules?

Typically, a module contains a bunch of subroutine definitions.  A
module may also contain code which is not part of a subroutine. This
code is executed at the time the module is loaded, so it can be used
to initialize the module. For example, the module might open
adatatbase connection or initialize some time at the time it is
loaded.


Such code might be successful, or it might fail. Perl allows the
module to indicate the result by returning a true or false value back
to its caller. If the value is false, Perl aborts the compilation
with an error message.

Unfortunately, the default return value is *false*, so a module which
just defines a bunch of subroutines, and which has no initialization
code, accidentally returns a false value back to the caller, and Perl
aborts. So we insert "1;" at the end to suppress this misbehavior.

http://dev.perl.org/rfc/269.pod
http://dev.perl.org/rfc/269.html

discusses this in some more detail.

For documentation, see perldiag:

%s did not return a true value
(F) A required (or used) file must return a true value
to indicate that it compiled correctly and ran its
initialization code correctly. It's traditional to
end such a file with a "1;", though any true value
would do. See the require entry in the perlfunc man-
page.

and the relevant part of 'perlfunc':

The file must return true as the last statement
to indicate successful execution of any initialization code, so
it's customary to end such a file with "1;" unless you're sure
it'll return true otherwise. But it's better just to put the
"1;", in case you add more statements.

Courtsey: http://lists.netisland.net/archives/phlpm/phlpm-2001/msg00426.html
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