Without seeing the code in ownmodule.pm and the error message, it's hard to tell. Incidentally all lowecase modules are reserved for pragmas, so even for an experiment you should use e.g. Ownmodule.

$ cat Ownmodule.pm
# -*- Perl -*-

use strict;
use warnings;

package Ownmodule;
use base 'Exporter';
our @EXPORT=qw/first/;

sub first {
    print "<first> called\n";
    second();
}

sub second {
    print "<second> called\n";
}

1;


__END__
$ perl -MOwnmodule -e first
<first> called
<second> called
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