Anyway, I read perlretut and since I still did not completely understood it, I also read perlrequick, Perl Intro regarding Regular Expressions, PerlFAQ6, Five Habits for Successful Regular Expressions, perlop, split and finally perlre.

This monastery has a lot more to offer in addition, to start with just what is listed in the Tutorials section: String matching and Regular Expressions, Quantifiers in regular expressions, Character Class Abbreviations, Pattern-matching examples, Split and join, Pattern Matching Exercises (and solutions), and more complex tutorials by chromatic, OM_Zen, Cody Pendant, diotalevi and Elian. Abigail-ii wrote numerous insightful nodes about regular expressions.

I should not forget to mention the books Mastering Regular Expressions and Regular Expression Pocket Reference.

And even though I think I don't understand it completely and also I certainly can't remember it all, I do practice it a bit and one day I might answer questions here about it.

I disagree that a referral to /c should be given near the /g info. Regular expressions are so very useful, that though complicated, they deserve close study, and since a lot of information is available for free in quite a readable and understandable manner, reading it will bring you quite some wisdom.