Three things to do with Perl

I have a CGI/Perl file that writes to a flat-file database (database.txt)
I would like that database to be cleared every day. Is there a way for Perl to interpret the time/date and clear the database if it is a day after the last date recorded?
I would also like it to note the time that the message was recorded in the flat file database.
And finally, how do I have Perl erase one part of the database.txt file when I ask it to through another Perl program?
Confusing isn't it? I'll try to explain it later if you are confused
Thanks a million
Nike_Guy_Man