I'd Use a hash to keep track of how many times the appears. A simple regex should be able to extract the field values. Something like

open(FILE, "./logfile.sql");
my %foo;

while (<FILE>) {

     my $index;
    
     if (m/Field0=(.*)\;/) {
       
         $index = $1;
     } else {

         # something didn't match correctly
         $index ="";
     }

     $foo{$index}++;
     if ($foo{$index} == 1) {

         # make insert statment

      } else {
         # make update statement.

      }

     

}
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Not as neat as ikegami solution but it should work