#MYFILE
if [ $me = you ]
then 
export ORA1=one
export ORA2=3f34
export ORA3=zzzz
fi


##</code><code>##

open MYFILE, "<$myfile";
 open COPYFILE, ">$copyfile";
  while(<MYFILE>){
if (m/(ORA3=)(\w+)/) { $value=$2 }
$value =~ s/$value/0/;
  print COPYFILE $_;
   }
   close MYFILE;
  close COPYFILE;

system (" mv COPYFILE MYFILE ");