Of course there is a way to do this. Computers are pretty smart nowadays. :)

You might try a Google Codesearch for routines called yesterday, or even just a normal googling of search.cpan.org for yesterday

Since this sounds a lot like a homework problem, you probaby won't be able to get away with using Date::Simple:

use Date::Simple qw(today);

$date = today() - 1;
    
print $date;
[download]

or Date::Manip:

use Date::Manip;

$date = ParseDate("yesterday");
    
print $date;
[download]

or Date::PeriodParser:

use Date::PeriodParser;

$date = parse_period("yesterday");
    
print scalar localtime( $date );
[download]

or many other modules which can handle this sort of thing. You can always look at their source to see how they did it.

Good luck :)