package common;

use strict;
use Exporter;
use CGI qw/:standard :delete_all :escapeHTML :html3 :all/;

# Setup to export common subroutines and variables used by many script
+s
our ( @ISA, @EXPORT_OK, $q );
@ISA = qw( Exporter );


@EXPORT_OK = qw( $query
                    is_tainted 
                    check_user 
                    authenticate
                    set_path
                    print_header 
                    print_footer 
                    error_form
                    log_msg 
                    );




# Instantiate a new CGI object
$query = CGI->new;

sub check_user {

....


}


sub is_tainted {

....


}


sub authenticate {

....


}

sub set_path {

....


}


sub print_header {

....


}


sub print_footer {

....


}


sub error_form {

....


}

sub log_msg {

....


}

1;
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use strict;

use lib "/path/to/lib";

use common qw( $query     
                    is_tainted 
                    check_user 
                    authenticate
                    set_path
                    print_header 
                    print_footer 
                    error_form
                    log_msg 
                     );

# Create query objects to retrieve input
my $username = $query->param( "user" );

# Display error message if the query objects are not found
unless ( defined $username )  {
    error_form( "<msg to display>" );
    exit;
}



# Set path
my $dir_path = set_path( $username );

# Check if $dir_path is set correctly
if ( $dir_path eq "Error" ) {
    error_form( "Error setting path" );
    exit;
}

# Authenticate
my $valid_code = authenticate( $username);

if ( $valid_code eq "FALSE" ) {
    log_msg( <messages> );
    error_form( "Invalid code" );
    exit;
}

#print the html page
print $query->header();
print $query->start_html(-title => 'Welcome', 
                    -bgcolor => 'white',
                    );
print_header( "Welcome" );    
print $query->start_form( -name => 'data', -action => 'page2' );
print $query->hidden( -name => "user", -value => $username );

...
etc..
...

print $query->end_form();
print $query->table( { -border=>0}, 
                    $query->Tr( [  $query->td( [ $query->a( {-href=>"j
+avascript:submitform()"}, 
                                    $query->img({-align=>"center", -sr
+c=>"submit.gif ", -border=>0 })) ]), 
                    ] ),
                );
print_footer();
print $query->end_html();
log_msg( <arguments> );
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