Looking for Patterns - Finding them with Regular Expressions

What are Regular Expressions (RE) Dos and Don’t of RE Languages where RE are available POSIX programs that use RE POSIX Basic and Extended RE grep and egrep usage RE literal characters RE dot (period) RE character classes RE named character classes RE carat anchor RE dollar sign anchor RE repetition RE asterisk RE plus sign RE question mark RE grouping RE alternation Perl character sequences Perl US Postal Code example Python Protocol example