perl -MSymbol -MData::Dumper -wE '
{my $x=gensym; print Dumper $x};
{my $y=gensym; print Dumper $y};
my $z=gensym; print Dumper $z;
print $x, $y'

##</code><code>##

Name "main::x" used only once: possible typo at -e line 1.
Name "main::y" used only once: possible typo at -e line 1.
$VAR1 = \*Symbol::GEN0;
$VAR1 = \*Symbol::GEN1;
$VAR1 = \*Symbol::GEN2;
Use of uninitialized value $x in print at -e line 1.
Use of uninitialized value $y in print at -e line 1.