#0  0x00002aaaae17f1f9 in tag_parser (tag=0x2 <Address 0x2 out of boun
+ds>, len=-1216936334, back_tag=0x7fffffc91ac7 "") at getandParseWithC
+_pl_05fd.xs:52
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shows that tag_parser is called with 2 for the first argument. That's obviously a bad pointer. The second argument is also obviously wrong.

One possibility is that the input is something like foo>bar, which would cause tag_parser to be called before ptag is ever initialized. Did you try dumping what parser_init returns and finding out to which char p points?

You're asking us to debug a C problem, you didn't provide any inputs, and you didn't provide any runnable code. The underlying cause could be a Perl problem, but you haven't gotten that far yet. Do you homework, then come back to us if it's Perl problem.

Update: Added some details.