Another handy trick (if you don't mind modifying the source and are focusing on a particular piece of code) is to set $DB::single to a true value which will act as if you'd put a breakpoint at that line.

Alternatives to the debugger proper: check out Smart::Comments which will let you get debugging dumps when you run using that module (it's a moderately ebil source filter, but unless you've enabled the module they're just plain text comments). Or use Log::Log4perl and liberally sprinkle DEBUG(qq{intresting value:}, $interesting) statements throughout your code; when you no longer need them, just reduce the log level to (e.g.) INFO instead and those disappear (but they're still there and can be turned back on at will by tweaking a config/log level).