my( $iUrl, $oUrl ) = @ARGS;
system "wget -qc -O $$.in $iUrl" and exit 1;
open I, '<', "$$.in" or exit 2;
open O, '>', "$$.out" or exit 3;
while( I ) {
    my $modified = ....
    print O $modified;
}
close I; 
unlink "$$.in";
close O;
system "wput -q $$.out $oUrl" or exit 4;
unlink "$$.out";
exit 0;