In attempting to decipher what your code is -- it appears that you have mismatched square-brackets and braces.

The closest to your code that compiles is:

$samstr = {source=>[{abc=>[{uname=>$VAR1,dbcrdn=>$VAR2,paridn=>$VAR3,o
+sath=>$VAR4,}]}]};
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Also : XML::Simple is a terrible module with inconsistent options.

Consider using an alternative, like XML::Twig.