As other monks have pointed out, Perl's regular expressions are indeed anything but regular in the formal sense. Formal regular expression use only the following operations:

• Concatenation: if a and b are regular expressions, then so is ab.
• Alternation: if a and b are regular expressions, then so is (a|b).
• The Kleene star: if a is a regular expression, then so is a*.

If you want to wrap your head around what these regular expressions really mean, though, it's best to start with formal languages, specifically regular languages. Regular expressions describe these languages in a very natural and obvious manner.

That said, while fascinating, none of this will help a lot with simplifying Perl regular expressions in a Perl program. For that, you'll need a good intuition of how regular expressions work in Perl, and for that you'll simply have to use them, time and again.

If you're not getting along with Mastering Regular Expressions, BTW, the chapter on regular expressions in Programming Perl is eminently readable and accessible.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.