open (FH, "<filename.txt") || die "could not open file: $!";
@ODB = <FH>;
close (FH);

$newline = "The new line of text to go at the top of the file";

open (NFH, ">filename.txt") || die "could not open file 2: $!";
print NFH "$newline" . "\n";
foreach $line (@ODB) {
print NFH "$line";
}
close (NFH);