Shell Programming and Scripting

This is going to be part of a longer script with more features, but I have boiled it down to the one thing that is presently stumping me. The goal is a script which checks for updates to web pages that can be run as a cron job. The script reads (from a tab-delim file) a URL, an MD5 digest, and an optional grep statement. (The idea of supplying a grep statement or grep parameters specific to each URL is to only look at the "interesting" parts of each page, ignoring ads, reader replies to blog posts, etc.) The script retrieves each page using curl, pipes it through the appropriate grep, then pipes through MD5, comparing the resulting digest to the MD5 digest already given in the file, and if different, activates an alert for that URL and stores the new MD5 back into the file. So here's what I have...

Contents of urls.test.ini (note fields separated by tabs)
==

Code:

http://www.sinfest.net    941f0f991ea9cd4c61ceb8cbf8833f81    grep comikaze
http://freefall.purrsia.com    f8af48b832c393b02993c18c87b6a47d    grep ff[0-9][0-9]*
http://twitter.com/spoonoftheday    3adc319c52e361e80cd2d7810a17181a    grep -o entry-content[^\<]*\<

Script code under test
==

Code:

OFS=$IFS
IFS="    " #tab character in the quotes
while read pageURL oldDigest filter
do
          echo "[$pageURL][$oldDigest][$filter]"
          newDigest=`curl -f -s -m 60 "$pageURL" | "$filter" | /sbin/md5`
          echo "$newDigest"
done < urls.test.ini
IFS=$OFS

Results
==
What this gives me is:

Code:

[http://www.sinfest.net][941f0f991ea9cd4c61ceb8cbf8833f81][grep comikaze]
prompt$: line 1: grep comikaze: command not found
d41d8cd98f00b204e9800998ecf8427e

(etc., similar for the rest of the data)

From this I conclude that:
1) The variables are at least all being read in correctly, with no extraneous characters, invisibles, etc.
2) The MD5 command is executing and $newDigest being assigned
3) Since the grep command is not being understood or executed (why?) the resulting digest is the MD5 for null.

Other things I have tried:
==
0) (Specifying bash vs. sh and back again)
1) Different quotings of the back ticks and variables including
newDigest="`curl -f -s -m 60 $pageURL | $filter | /sbin/md5`"
and
newDigest=`curl -f -s -m 60 $pageURL | $filter | /sbin/md5`
2) Specifying /usr/bin/grep in the .ini file. Error message THEN is the grep statement kicked back but saying "File not found", suggesting that grep is being run in the pipe, but it is misunderstanding and choking on the arguments
3) Separating out the arguments, with ONLY the params in the .ini file:
newDigest="`curl -f -s -m 60 $pageURL | grep $filter | /sbin/md5`"

That last variation almost works. It returns the correct MD5 digest for the first two lines of the example data, but chokes on the third one, saying "-o entry-content[^\<]*\< -- no such file", the difference no doubt being the initial hyphen, and incorrectly trying to read the -o flag as part of the pattern.

Any thoughts? It seems so simple, all I want the script to do is assign a variable the result of...
$ curl -options URL | grep -FLAGS PATTERN | md5
(which all works fine done manually at a shell prompt) but with URL, FLAGS and PATTERN being read in from a separate file.

Any insights/guidance will be most appreciated, thanks in advance. --JMF

PS: If I do this in Perl, the statement
chomp ($newDigest = `curl -f -s -m 60 $url | $filter | /sbin/md5`)
works perfectly!! However, I really want to write this in pure shell script as opposed to Perl, because I think I can get the overall script cleaner and more portable, if the dang thing would only WORK.

put grep regexp rule always to between " ", because before grep shell get the arguments, shell try to parse those special things like: * $ ( ) ? > < ... are very often parsed before grep.

using echo before command is nice debug, you can see howto shell parse the line
echo cmd arguments

eval is often answer in this kind of needs, something like:
cmd="some \"arg1\" \"arg2\" "
eval $cmd
eval = parse cmdline twice.

1. some \"arg1\" \"arg2\" =>
some "arg1" "arg2"
2. parse, previous line looks good = "normal" commandline