DB<100> sub tst {}
 => 0

##</code><code>##

$ perl -e 'use Data::Dumper; print Dumper eval "sub tst {}"'
$

##</code><code>##

$ perl -e 'use Data::Dumper; print Dumper eval "\$^D=\$^D;sub tst {}"'
$VAR1 = '0';

##</code><code>##

$evalarg = "\$^D = \$^D | \$DB::db_stop;\n$cmd";

##</code><code>##

$evalarg = "\$^D = \$^D | \$DB::db_stop;\ndo {$cmd}";

##</code><code>##

:~$ perl -e 'use Data::Dumper; print Dumper eval "\$^D=\$^D;do {sub tst {}}"'
:~$