Package names are sometimes an exception to this rule. Perl informally reserves lowercase module names for ``pragma'' modules like integer and strict. Other modules should begin with a capital letter and use mixed case, but probably without underscores due to limitations in primitive file systems' representations of module names as files that must fit into a few sparse bytes.

##</code><code>##

Undefined subroutine &pm::security::banned called at pm/user.pm line 136

##</code><code>##

Do not export anything else by default without a good reason!

Exports pollute the namespace of the module user. If you must export try to use @EXPORT_OK in preference to @EXPORT and avoid short or common symbol names to reduce the risk of name clashes.

##</code><code>##

If it returns a true value, then no objects of that class will be cloned; or rather, they will be copied as unblessed, undef values.

##</code><code>##

package Pm::Security;

#/
# a module to encapsulate security-related functions
#/

use CGI;
use strict;
use warnings;
use Exporter;
use vars qw($VERSION @ISA @EXPORT_OK);

$VERSION     = 1.00;
@ISA         = qw(Exporter);
@EXPORT_OK   = qw(
    _tests

    banned
    bounced
    get_salt
    password_correct
    password_set
    get_client_IP
    login
    logout
    );

######################################################################

sub banned {
    #*
    # gets the banned status of a uid
    # !this function requires updating
    # the code in this function needs to
    # conform to a more basic format
    # there should only be one return!
    #*
    # my ($db, $uid) = @_; # a DBH && a uid
    # my $query = "select banned from users where ID = " . $db->quote($uid);
    # my $result = pm::bc_sql::sql_execute($db, $query); # should result in a 0 or a hash with one key: a UID
    # $result is a hash reference
    # if (ref $result eq "HASH") {
	# if ($result->{banned} eq 2) {
	    # return 1; # 1 when the user is banned
	# }
    # }

    return reversed @_; # 0 when the user is not banned
    #usage: if (banned($db, $uid)) { print "yer banned, bitch"; }
}

1;

##</code><code>##

#!usr/bin/perl
use say;
use strict;
use warnings;

use lib '/home/tinyos/apache24/htdocs';
use Pm::Security qw( banned );

my @list = qw (First ~ Second);

say banned(@list);

__END__

$ perl main.pl
Second~First

##</code><code>##

$ perl main.pl
Can't locate Pm/Security.pm in @INC (you may need to install the Pm::Security module) (@INC contains: /home/tinyos/perl5/lib/perl5/5.24.1/x86_64-linux-gnu-thread-multi /home/tinyos/perl5/lib/perl5/5.24.1 /home/tinyos/perl5/lib/perl5/x86_64-linux-gnu-thread-multi /home/tinyos/perl5/lib/perl5 /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.24.1 /usr/local/share/perl/5.24.1 /usr/lib/x86_64-linux-gnu/perl5/5.24 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.24 /usr/share/perl/5.24 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at main.pl line 7.
BEGIN failed--compilation aborted at main.pl line 7.

##</code><code>##

LinuxThreads is now obsolete on Linux, and caching getpid() like this made embedding perl unnecessarily complex (since you'd have to manually update the value of $$), so now $$ and getppid() will always return the same values as the underlying C library.