use threads;

my $x=1;

my $threads = threads->new(sub {eval '(++$x)+1'});
print "The value of \$x before eval is $x\n";
my $val = $threads->join();
print "The eval returned $val\n";
print "The value of \$x after eval is $x\n";

##</code><code>##

The value of $x before eval is 1
The eval returned 3
The value of $x after eval is 1