If stepping through the program in Perl debugger doesn't help, try opening STDOUT/STDERR to some log file ("/tmp/$$.log", for example) or writing a __DIE__ signal handler:

sub {
 return unless defined $^S; # bail out if it's a parser error
 open my $log, ">/tmp/crash@{[time]}_$$.log";
 print $log @_;
}
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