Here's an alternative method involving grep and split:

local $/;

my $data = <DATA>;
my @found = grep /^[IO]/ => split /\n/ => $data;
print map { join '' => $_, "\n", } @found; # or whatever.

__DATA__
group: device_info
In    ; 10 ; 0x0 ; 0x100cd ; .1
Out    ; 10 ; 0x0 ; 0x100d3 ; .1
In    ; 20 ; 0x0 ; 0x500c4 ; .1
Out    ; 20 ; 0x0 ; 0x500d4 ; .1


data: None
[download]