# loop starts upward of here
# $key must be scoped outside the loop
    chomp;
    if (/^\d+\.\d+\.\d+\.\d+$/) {
        next unless $key;
        push @{$CoreRegR{$key}}, $_;
        # Alt. replace the prev 2 lines with
        # push @{$CoreRegR{ $key || 'unnamed host' }}, $_;
    }
    else {
        $key = $_
    }
# ...