The difference is that MySQL runs as a server and accesses a directory to store its database, and SQLite is library that reads a single file.

DBD::mysql connects to the server (localhost), chooses a database (nehnu), which is mapped to a disk location (c:/MySQL/Data/database), and logs in with a user (root). The DSN contains all that info:

DBI->connect("dbi:mysql:nehnu;localhost", "root", "");
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DBD::SQLite opens the database file. The DSN just needs the filename:

DBI->connect("dbi:SQLite:/SQLite/Data/database.sqlt");
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