Well, considering this is perlmonks, not sedmonks, I can give you a solution that happens to use perl intrinsically rather than spawning sed.

   open F1, "< $write" or die $!;
   open F2, "> $write2" or die $!;
   while (<F1>) {
     s/$search/$replace/ig;
     print F2 $_;
   }
   close F1;
   close F2;
[download]

Depending on what you're doing, you might be able to avoid the external files altogether.

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.