Manipulating certain lines of a file in Perl - regex

Question

This is basically a question regarding file manipulation. I'm working on a Perl script that will run as a cron job that sends an email when certain values shows up on a web page, but does so only once until the value resets (it's a page of reports containing audits that show an alert when a report requires attention). I've figured out how to parse the page for alerts, I know how to send emails via Perl, I'm just having a hard time figuring out the logic for WHEN to send the email. I gather that a separate file (alerts.txt) will need to be created to store the reports that had an alert during the previous execution of the script. In that case you have 4 scenarios to handle in the script. 1) The report has an alert and isn't in alerts.txt (needs to be added). 2) The report doesn't have an alert but is in alerts.txt from a previous execution of the script (needs to be removed). 3) The report doesn't have an alert and isn't in alerts.txt (do nothing). 4) The report has an alert and is already in alerts.txt (do nothing).
Is this the best way to go about this? If so, what's the best way to implement scenarios #1 and #2 above?

Answer 1

I am assuming you've chosen not to use a database - which is valid in some situations but you may change your mind as your application grows.
The simplest method, is to use the Storable modules which comes built in with perl. Note, this produces non human readable formats but can store quite complex data structures;
#!/usr/bin/env perl
use Storable;
# Create some alerts data, and store it in a data file
my $alerts = {};
$alerts->{report_01} = 'alert';
$alerts->{report_02} = 'ok';
store $alerts, 'alerts.data';
# Read it back
my $prev_alerts = retrieve('alerts.data');
foreach my $key (keys %$prev_alerts) {
print "$key=$prev_alerts->{$key}\n";
}
If you desire a human readable format there are various options that support file based storage;
ini; Config::Tiny
xml; XML::Simple
csv; Text::CSV