"I was born in 270", proclaimed St Nick, "and I thought I'd seen everything. Until now that was."

Santa was staring into the source code for creating the naughty or nice list. The very definition of legacy system, the codebase hadn't faired well when the latest round of refactoring had been outsourced to the tooth fairies.

"This just shows we should never again go with the lowest bidder…" the Wise Old Elf sagely commented. "…even if they do only want payment in an excessive number of candy canes for unspecified purposes."

"Ho ho ho! The problem is we've now got two functions called 'present'. One that renders out part of the list, and one that refers to if the child should get a gift or coal. I suppose you've got a plan that's better than working out by hand which is which during the big search and replace?"

"Of course, your Jollyness, I'm going to use Perl to print out which one is used where", the Wise Old Elf explained.

"Ah the old 'caller' technique where you alter the functions to say where they're being called from"

# in Santa::NaughtyOrNice::Gift
sub present {
    {
        my ($package, $filename, $line) = caller;
        say STDERR "present (as in gift) called at $filename line $line";
    }
    ...
}

# in Santa::NaughtyOrNice::Render
sub present {
    {
        my ($package, $filename, $line) = caller;
        say STDERR "present (as in render) called at $filename line $line";
    }
    ...
}

"No, your Festiveness", the Wise Old Elf replied, "That'd only print out when the functions in question are executed. But there's functions that aren't called every run of the program — why, here's some code that declares someone as naughty if they troll on MySpace. I bet that doesn't come up every day anymore".

"My intention", the Wise Old Elf continued, "is to instead hook the compilation stage of Perl to print out when the subroutine is used as soon it's compiled. There's a module for that you know…

  perl -c \
       -MDevel::CompiledCalls=Santa::NaughtyOrNice::Render::present \
       -MDevel::CompiledCalls=Santa::NaughtyOrNice::Gift::present \
       naughty_or_nice.pl
   Santa::NaughtyOrNice::Render::Gift::present call at /santa/lib/Santa/NaughtyOrNice/HairPulling.pm line 13
   Santa::NaughtyOrNice::Render::Gift::present call at /santa/lib/Santa/NaughtyOrNice/HairPulling.pm line 49
   Santa::NaughtyOrNice::Render::Render::present call at /santa/lib/Santa/NaughtyOrNice/Report.pm line 41
   Santa::NaughtyOrNice::Render::Gift::present call at /santa/lib/Santa/NaughtyOrNice/SignificantWhitespace.pm line 134
   Santa::NaughtyOrNice::Render::Gift::present call at /santa/lib/Santa/NaughtyOrNice/BadOrGood.pm line 1041
   ...

See Also

• Devel::CompiledCalls