In perl, is there a way to make subroutines print their name and arguments when called?

Question

I need to quickly understand which subroutines are being called in a mess of spaghetti code perl modules.

I could write a script to go through all the modules and add code to print out the subroutine name and arguments at the start of every subroutine.

But is there a way to override the internal perl 'subroutine' mechanism itself to do this?

The code is running under mod_perl so I can't easily use a debugger.

Answer 1

You could use Moose::MethodModifiers. I don't know much about Moose, but from the manual I can see you can do it. Here goes.

#!/usr/bin/perl -w
use 5.010;
use strict;
use Moose;

sub sub_one {
    say "I am sub one!";
}

sub sub_two {
    say "Guess who!";
}

# Note that the name of the function being modified isn't passed in in
# any way

for my $func qw(sub_one sub_two) {
    around $func => sub {
        my $orig = shift;

        say "Running ${func}(@_)";

        # call the original sub
        my $self = shift;
        $self->$orig(@_);
    }
}

sub_one(21, 12);
sub_two();

This produces something like

cnicutar@aiur:~$ perl method_modifiers.pl
Running sub_one(21 12)
I am sub one!
Running sub_two()
Guess who!

Please note I'm only a beginner so be cautious about that code.