open; split and on-and-on....
or, if your learning style is compatible with examples...check Super Search for threads here dealing with the issues you face, and see also http://www.perlmonks.com/index.pl?node=Tutorials#Input-and-the IO tut in our Tutorials section.
But a couple points about your question:
- Is the data sample you posted an example of a single line (record) in data.txt or are each of the label:value pairs on a separate line or something else entirely? (Implicit hint made explicit: your questions will generally get quicker and better help if your problem statement is precise.)
- Your question suggests that you might hope to learn Perl by studying the syntax of some functions. That's probably sub-optimal. The "chapters" element is likely a better route, and which text to recommend depends (to some extent) on the extent your prior experience as a programmer.
But without that info, it's hard to do better than recommending Learning Perl, 6th ed. But beware: the first several hits if you simply Google the title appear to be UNauthorized ... ie, ripoffs of the authors and O'Reilly.
Edits for fact, spelling and references. Aaagh!