The question is : what kind of db?

SELECT * FROM guests ORDER BY time DESC LIMIT 50

This is the sql line that's used for getting the first 50

In cgi I would make from 50 a variable so if somebody's pushes next(50) the variable would add 50.

Don't know how it's just done in perl. But I connected to the db with php to get what you wanted.

The best hint I can give is. Search on CPAN for DBI. Look to the perl-syntax how to connect to a db.
But most important is to know sql-syntax. Only then you can learn how to program databases(in any programming language).
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but not the fact that I am right