What do you get if you inspect $@ in case an error is thrown?  (IIRC, the error messages do include line number information.)

Update: for example, when I add the line

print $@ if $@;
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to your code snippet, and with a sample.xml containing

<?xml version="1.0" encoding="UTF-8"?>
<mydoc>
<foo>
<bar>...
</bar_>
</foo>
</mydoc>
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I do get:

$ ./840913.pl
sample.xml:5: parser error : expected '>'
</bar_>
     ^ at ./840913.pl line 11
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