Stefan mentioned SED and AWK, which are both command-line text manipulation tools.  SED is the simplest, and is best used for regular expression search and replace.  AWK is its own little programming language, and is a more powerful than SED, but much lighter than Perl.

I spent a lot of time exploring text manipulation tools a few years back.  I ended up using AWK and Perl for most things, but then I found Datamystic's TextPipe Pro (shareware, $299) http://snipurl.com/leapfrog_textpipe, for it's power and ease of use.  I became such a fan of the product that I have since become a reseller.

I might be able to work out a discount deal on TextPipe for DonationCoder members only... Mouser, I will contact you about this offline.

I use Regex Coach (free) to help me with tough regular expressions.
http://www.weitz.de/regex-coach/

The Regex Coach is a graphical application for Linux and Windows which can be used to experiment with (Perl-compatible) regular expressions interactively. It has the following features:

    * It shows whether a regular expression matches a particular target string.
    * It can also show which parts of the target string correspond to captured register groups or to arbitrary parts of the regular expression.
    * It can "walk" through the target string one match at a time.
    * It can simulate Perl's split and s/// (substitution) operators.
    * It tries to describe the regular expression in plain English.
    * It can show a graphical representation of the regular expression's parse tree.
    * It can single-step through the matching process as performed by the regex engine.
    * Everything happens in "real time", i.e. as soon as you make a change somewhere in the application all other parts are instantly updated.

How about a system volume scheduler? 

I hate it when I hit a web site with a loud midi background theme at 2 AM and wake up everybody in the house.

The interface could be a little line-chart, with volume % vertically and hours of the day horizontally.  The user could draw the volume level by drawing a line across the chart.