open( my $old, '<', 'current.log'     ) or die "ack: $!";
open( my $new, '>', 'current.log.new' ) or die "ack: $!";

print {$newfh} $your_data_here;
print {$newfh} $_ while <$old>;

close $old;
close $new;

rename 'current.log.new', 'current.log';