#!/usr/bin/env perl

use strict;
use warnings;

while (my $init_line = <DATA>) {
    my $neg_class_line = $init_line;
    my $neg_assert_line = $init_line;

    $neg_class_line  =~ s/,([^,]*)$/$1/;
    $neg_assert_line =~ s/,(?!.*,)//;

    print 'Initial line:       ', $init_line;
    print 'Negated class:      ', $neg_class_line;
    print 'Negative assertion: ', $neg_assert_line;
    print '-' x 40, "\n";
}

__DATA__
21112,/vol/voly,blx
21113,/vol/eng,blz
21114,/vol/eng,file

##</code><code>##

Initial line:       21112,/vol/voly,blx
Negated class:      21112,/vol/volyblx
Negative assertion: 21112,/vol/volyblx
----------------------------------------
Initial line:       21113,/vol/eng,blz
Negated class:      21113,/vol/engblz
Negative assertion: 21113,/vol/engblz
----------------------------------------
Initial line:       21114,/vol/eng,file
Negated class:      21114,/vol/engfile
Negative assertion: 21114,/vol/engfile
----------------------------------------

##</code><code>##

W,X,Y,Z
W,X,YZ
W,XYZ
WXYZ

##</code><code>##

Initial line:       W,X,Y,Z
Negated class:      W,X,YZ
Negative assertion: W,X,YZ
----------------------------------------
Initial line:       W,X,YZ
Negated class:      W,XYZ
Negative assertion: W,XYZ
----------------------------------------
Initial line:       W,XYZ
Negated class:      WXYZ
Negative assertion: WXYZ
----------------------------------------
Initial line:       WXYZ
Negated class:      WXYZ
Negative assertion: WXYZ
----------------------------------------