I'm having trouble getting Perl 5.10 features working in the Perl debugger.

I'm using Perl 5.12.3 on Red Hat Enterprise Linux 6, starting the debugger with the following line:

and I get the following error when I run say "Hey";

String found where operator expected at (eval 11)[/s/perl-5.12.3/amd64
+_rhel6/lib/5.12.3/perl5db.pl:638] line 2, near "say "Hey""
 at (eval 11)[/s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5db.pl:638] li
+ne 2
        eval '($@, $!, $^E, $,, $/, $\\, $^W) = @saved;package main; $
+^D = $^D | $DB::db_stop;
say "Hey";;

;' called at /s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5db.pl line 638
        DB::eval called at /s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5
+db.pl line 3448
        DB::DB called at -e line 1
        (Do you need to predeclare say?)
 at (eval 11)[/s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5db.pl:638] li
+ne 2
        eval '($@, $!, $^E, $,, $/, $\\, $^W) = @saved;package main; $
+^D = $^D | $DB::db_stop;
say "Hey";;

;' called at /s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5db.pl line 638
        DB::eval called at /s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5
+db.pl line 3448
        DB::DB called at -e line 1
syntax error at (eval 11)[/s/perl-5.12.3/amd64_rhel6/lib/5.12.3/perl5d
+b.pl:638] line 2, near "say "Hey""
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Doing use '5.12.0', or use feature ':5.12' doesn't help either. How can I get this to work?