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When debugging warnings from the perl core like Use of uninitialized value ... let the debugger pause right there. Then have a good look at the context that led to this situation and investigate variables and the callstack.

To let the debugger do this automatically I use a debugger customization script:

sub afterinit { $::SIG{'__WARN__'} = sub { my $warning = shift; if ( $warning =~ m{\s at \s \S+ \s line \s \d+ \. $}xms ) { $DB::single = 1; # debugger stops here automatically } warn $warning; }; print "sigwarn handler installed!\n"; return; }
Save the content to file .perldb (or perldb.ini on Windows) and place it in the current or in your HOME directory.

The subroutine will be called initially by the debugger and installs a signal handler for all warnings. If the format matches one from the perl core, execution in the debugger is paused by setting $DB::single = 1.

In reply to Re: Basic debugging checklist by hexcoder
in thread Basic debugging checklist by toolic

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    [MidLifeXis]: heh.
    [MidLifeXis]: Most likely it is a code that some undocumented system, hidden behind layers of IT, deep in the bowels of the building under the machine room floor, reads that code to keep a presence switch from going off. :-b
    [MidLifeXis]: I think I forgot "running on a farm of commodore 64, vic 20s, trs 80s, and apple ]|[e systems"
    [GotToBTru]: oh I know what it is .. but it is a number only slightly useful to me and of no possible use to our customer
    [MidLifeXis]: Whew - you just saved the free world. <o)
    [GotToBTru]: i guess it's a placeholder, the code will only fill it in if there is nothing else to use

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