Hmmm...

my %all_the_stuff = ();

my $current;
while( <> ){
    chomp;
    next unless length;

    if( m/^KEY: (.+)/ ){
       $current = {
            OID   => [], #you migth want to put these two
            NAME  => [], # together, i don't know
            ERROR => undef,
       };
       $all_the_stuff{ $1 } = $current
    }

    next unless $current;

    if( m/^(OID|NAME): (.+)/ ){
       push @{$current->{$1}},$2
    }
    elsif( m/^Error Status (.+)/ ){
       $current->{ERROR} = $1;
       $current = undef; #error status is final statement
    }
}
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See perlref,perllol, perldsc and perhaps perlre. The code is untested and not to be used without careful analysis.