my $x = 999;
my $r1 = \$x;
my $r2 = $r1;
print "\$r1=$r1\t\$r2=$r2\t\$\$r1=$$r1\t\$\$r2=$$r2\n";
$x = 111;
print "\$r1=$r1\t\$r2=$r2\t\$\$r1=$$r1\t\$\$r2=$$r2\n";
${$r1} = 555;
print "\$r1=$r1\t\$r2=$r2\t\$\$r1=$$r1\t\$\$r2=$$r2\n";
${$r1} = 777;
print "\$r1=$r1\t\$r2=$r2\t\$\$r1=$$r1\t\$\$r2=$$r2\n";