Is this a bug in Perl?

cog on 2004-12-31T00:33:09

I can't do this:

#!/usr/bin/perl
use strict
print "Hello World\n"

but I can do this:

#!/usr/bin/perl
use integer
print "Hello World\n"

I can't do this:

#!/usr/bin/perl
use Lingua::Identify
print "Hello World\n"

but I can do this:

#!/usr/bin/perl
use Date::Easter
print "Hello World\n"

Exactly... what is going on around here? :-)

Preliminary testing seemed to reveal that the reason it would only work sometimes would be that it only worked when the module version number was equal or above 1 (see * in the bottom, for the reason), but there were exceptions (strict 1.03 not working and CPAN::Mini 0.20 working, for instance).

Finding the solution would probably involve looking into the modules, which I don't think I'm able to after the day I had :-)

This seems rather odd... :-)

* - a sample error:

Lingua::Identify version 1 required--this is only version 0.10 at usr/lib/perl5/5.8.4/Exporter/Heavy.pm line 121.
BEGIN failed--compilation aborted at ./script line 3.

---

$title =~ s/Perl/perl/

cog on 2004-12-31T00:34:07

Subject says it all... O:-)

consult perldoc

rjbs on 2004-12-31T00:50:28

One signature for use is "use Module VERSION"

You can use an expression for VERSION, even though the manual isn't crystal clear on that. A little testing goes a long way.

print returns 1 on success, so you're trying to use that module with version 1 or more.

Re:consult perldoc

cog on 2004-12-31T00:56:12

That makes sense. Now that I think about it, I don't know how I didn't get it at first...

But come to think about it again, what about CPAN::Mini (version 0.20) and strict?

Wait... strict was giving a different error...

I need to get some sleep... over and out, back again sometime tomorrow... :-)

All perfectly normal, nothing to see, move along

Aristotle on 2004-12-31T14:32:18

It all depends on the &import of a module.

Lingua::Identify uses Exporter which considers the parameter a version number and croaks because it's higher than the module's.

strict uses a custom importer which considers the number a non-existant pragma tag and croaks.

In case noone else defines an &import, modules inherit &UNIVERSAL::import. Interestingly, that one does differentiate between a literal number and an expression:

$ echo 'package Foo; our $VERSION = 0.1; 1;' > Foo.pm
$ perl -le'BEGIN { $a = 1 } use Foo $a'
$ perl -le'use Foo print'

$ perl -le'use Foo 1'
Foo version 1 required--this is only version 0.1 at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

Re: Is this a bug i Perl?

uniejo on 2005-01-01T20:55:31

You need a semi colon after the use statement.
Without that you only have one statement:

#!/usr/bin/perl
use strict   print "Hello World\n"

The return of the print statement is 1 (unless it fails).
This effectively changes it into use strict 1.0 , whereby the module is required to be at least version 1.0

Of course your code should look like this:

#!/usr/bin/perl
use strict;
print "Hello World\n";


Re: Is this a bug i Perl?

cog on 2005-01-01T21:15:05

That was the precise point, the fact that the code would work some of the times without the semicolon :-)

The part of the version one was taken care of pretty quickly, but it took Aristotle to find out the reason for the exceptions (that is, modules below version 1 working and vice-versa).

You wouldn't believe how ashamed of myself I am for not having solved the problem before posting it... oh well, one learns new things everyday :-)

Anyway, if that's what it takes to bring a new user to the site, you can all count of me to do it again... O:-)

Cheers, and welcome :-)