use XML::Simple qw(XMLout);
$samstr =  source=>[{abc=>[{uname=>[$VAR1],dbcrdn=>[$VAR2],paridn=>[$VAR3],osath=>[$VAR4],}]
$xmlstr = "{".$samstr."}";
print XMLout($xmlstr,RootName => "root");

##</code><code>##

$xmlstr = {
              source=>[{abc=>[{uname=>["USER"],dbcrdn=>["PWD"],paridn=>["XYZ"],osath=>["0"],}]
           }

print XMLout($xmlstr,RootName => "root");