It's impossible to say from the warning messages what the problem is, since it's occuring inside some anonymous eval statement. However, you can set up a handler for warnings that will print out a stack trace, showing where in the code this particular eval can be found, and the path your program took to get to it.
$SIG{__WARN__} = sub {
warn @_;
my $i = 0;
while (my($pkg, $file, $line) = caller($i++)) {
warn " package $pkg, file $file, line $line\n";
}
};