+
+# Allow name of digits/underscores only if it begins with underscore
+{
+ use warnings FATAL => 'constant';
+ eval q{
+ use constant _1_2_3 => 'allowed';
+ };
+ ok( $@ eq '' );
+}
+
+sub slotch ();
+
+{
+ my @warnings;
+ local $SIG{'__WARN__'} = sub { push @warnings, @_ };
+ eval 'use constant slotch => 3; 1' or die $@;
+
+ is ("@warnings", "", "No warnings if a prototype exists");
+
+ my $value = eval 'slotch';
+ is ($@, '');
+ is ($value, 3);
+}
+
+sub zit;
+
+{
+ my @warnings;
+ local $SIG{'__WARN__'} = sub { push @warnings, @_ };
+ eval 'use constant zit => 4; 1' or die $@;
+
+ # empty prototypes are reported differently in different versions
+ my $no_proto = $] < 5.008 ? "" : ": none";
+
+ is(scalar @warnings, 1, "1 warning");
+ like ($warnings[0], qr/^Prototype mismatch: sub main::zit$no_proto vs \(\)/,
+ "about the prototype mismatch");
+
+ my $value = eval 'zit';
+ is ($@, '');
+ is ($value, 4);
+}
+
+$fagwoosh = 'geronimo';
+$putt = 'leutwein';
+$kloong = 'schlozhauer';
+
+{
+ my @warnings;
+ local $SIG{'__WARN__'} = sub { push @warnings, @_ };
+ eval 'use constant fagwoosh => 5; 1' or die $@;
+
+ is ("@warnings", "", "No warnings if the typeglob exists already");
+
+ my $value = eval 'fagwoosh';
+ is ($@, '');
+ is ($value, 5);
+
+ my @value = eval 'fagwoosh';
+ is ($@, '');
+ is_deeply (\@value, [5]);
+
+ eval 'use constant putt => 6, 7; 1' or die $@;
+
+ is ("@warnings", "", "No warnings if the typeglob exists already");
+
+ @value = eval 'putt';
+ is ($@, '');
+ is_deeply (\@value, [6, 7]);
+
+ eval 'use constant "klong"; 1' or die $@;
+
+ is ("@warnings", "", "No warnings if the typeglob exists already");
+
+ $value = eval 'klong';
+ is ($@, '');
+ is ($value, undef);
+
+ @value = eval 'klong';
+ is ($@, '');
+ is_deeply (\@value, []);
+}