Does $DB::doccmd='perldoc' do what you want? Seems to work OK for me with 5.10.0: 
-> perl -de0

main::(-e:1):   0
  DB<1> $DB::doccmd='perldoc'

  DB<2> perldoc -f grep

[download]
shows me the usual perldoc -f grep output

In reply to Re: [perldebugger] calling perldoc from within the debugger by broomduster
in thread [perldebugger] calling perldoc from within the debugger by LanX

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