Perl use module, keep getting Undefined subroutine &main error

Question

I have a perl module DB.pm, inside is somthing like:

package GUI::DB;
use strict;
use DBI;
use vars qw(@ISA @EXPORT);
use Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(fun);
sub fun {
    my $dsn = "DBI:mysql:database=test";
    return $dsn;
}

Then I wrote test.pl:

#!/usr/bin/perl
use strict;
use warnings;
use lib '~/Downloads/GUI'; #Here is the path of the DB.pm module.
use DB;
my $aa = fun();

I have been trying to fix it for hours, I tried to use comment perl -l /path/to/file aa.pl and it gave me no error but the script didn't run at all, I am purely new to Perl, really stuck. Please help me.

EDIT: So the module's name is DB.pm and folder's name is GUI now, and I an using use DB in my script, still doesn't work, where should I save the DB.pm file?

The convention is to define a package called `GUI::DB` in a file called `GUI/DB.pm`, and to import it with `use GUI::DB` to avoid the very problems you are having. — mob, Oct 31 '13 at 22:20
I changed the folder name to GUI, counld not name a file with '/', and now it give me `Can't locate GUI/DB.pm in @INC (@INC contains: ~/Downloads/GUI /etc/perl ...the lib paths..` — bathpp, Oct 31 '13 at 22:33
you need to `mkdir aaa ` to make the directory before renaming it — justintime, Nov 01 '13 at 05:12
`~` is not expanded by perl. Use $ENV{HOME} instead if you're on a Unix system. — Slaven Rezic, Nov 01 '13 at 06:50

score 4 · Answer 1 · answered Oct 31 '13 at 22:37

4

use HA; does a couple of things. First, it finds a file HA.pm in the perl library paths (@INC). Second, it calls HA::->import() to allow the HA module to do whatever initialization/exporting it wants; this relies on the module's package matching its filename. If it doesn't, this initialization is quietly skipped (method calls to an import method don't generate an error even if the method does not exist).

So explicitly call import on the package you want, or make the package name match the filename.

answered Oct 31 '13 at 22:37

ysth

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I changed the module's name to DB.pm, and I an using use DB(also GUI::DB) in my script, i also tried my $aa= DB->fun();still doesn't work, where should I save the DB.pm file? – bathpp Oct 31 '13 at 22:56
normally perl will look for modules in the current directory, in addition to other places. does `perl -wle'print for @INC'` show `.` as one of rows? if so, put DB.pm under ./GUI/ – ysth Nov 01 '13 at 00:08

score 3 · Answer 2 · edited May 23 '17 at 12:21

3

Perl doesn't understand ~, see How do I find a user's home directory in Perl?

You also need to give use lib the directory which GUI/DB.pm is in and use GUI::DB:

use lib $ENV{HOME}."/Downloads";
use GUI::DB;

edited May 23 '17 at 12:21

Community

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answered Nov 01 '13 at 07:38

RobEarl

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Perl use module, keep getting Undefined subroutine &main error

2 Answers2