If you want to keep debugging code in the production codebase, which may often be a good idea, I thought up a nifty idea, although I've never implemented it:

sub debug ($) {0;} # constant subroutine gets inlined for speed

sub set_debug {
  # set your options...
  no warnings;
  *{My::Package::debug}{SUB} = sub {
    # your debugging subroutine goes here
  }
}
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The idea being that unless set_debug is called, your debug calls don't take up any time because they are inlined by the compiler. For this you do require (1) constant-length argument lists to your debug subroutine and (2) NOT using a debug 'object', because then (I think) subroutine argument signatures don't work.

andramoiennepemousapolutropon