Hmmm... there are two cases: with or without running the debugger. I assume you meant the case without the debugger.

No, I meant what I said. $DB::deep has no effect on the warning. Ever.

With the debugger, one can set the threshold higher than 100 interactively prior to running the program

That's not true.

>perl -dwe"$DB::deep = 1000; sub f { f($_[0]-1) if $_[0]; } f(150);"

Loading DB routines from perl5db.pl version 1.37
Editor support available.

Enter h or 'h h' for help, or 'perldoc perldebug' for more help.

main::(-e:1):   $DB::deep = 1000; sub f { f($_[0]-1) if $_[0]; } f(150
+);

  DB<1> r
Deep recursion on subroutine "main::f" at C:/Progs/perl5161-ap1601/lib
+/perl5db.pl line 3550.
 at C:/Progs/perl5161-ap1601/lib/perl5db.pl line 3550.
...
[download]

See the post to which you replied if you want to know what $DB::deep actually does.