#! perl
use strict;
use warnings;

my $s = 'fred';
print "\$ = $s\n";
$s = 'barney';
print "\$s = $s\n";
Internals::SvREADONLY($s, 1);
$s = 'wilma';
print "\$ = $s\n";

##</code><code>##

19:04 >perl 723_SoPW.pl
$s = fred
$s = barney
Modification of a read-only value attempted at 723_SoPW.pl line 10.

19:07 >

##</code><code>##

#! perl
use strict;
use warnings;

my $s = 'fred';
print "\$s = $s\n";
$s = 'barney';
print "\$ = $s\n";
Internals::SvREADONLY($s, 1);
Internals::SvREADONLY($s, 0);
$s = 'wilma';
print "\$ = $s\n";

##</code><code>##

19:10 >perl 723_SoPW.pl
$s = fred
$s = barney
$s = wilma

19:12 >

##</code><code>##

#! perl
use strict;
use warnings;

for my $s ('fred')
{
    print "\$s = $s\n";
    Internals::SvREADONLY($s, 0);
    $s = 'wilma';
    print "\$ = $s\n";
}

##</code><code>##

19:14 >perl 723_SoPW.pl
$s = fred
Modification of a read-only value attempted at 723_SoPW.pl line 9.

19:16 >