regex, negations, grep, find and replace (a few questions)

Here is a regex to match a link. Testing the regex using echo and
piping it
$ echo "abc<a href=\"http://www.blah.com\";>click here</a>" | grep -P
'<a href="http://www.*>.*</a>'

a)
A problem is that grep works line by line. So
- it includes the abc before the link
- if the pattern/link were broken over 2 lines, it would not match
(other tests suggest that)

I really don`t want it to include the abc at the beginning of the line
where the pattern matches.

Is there anything like grep that does not have this problem/feature ?
or where that problem/feature can be turned off?

b)
I heard that it is hard to negate a regex.
So, alternatives,
some programming languages provide advanced features to negate it.
Also, programs, like grep, allow you to negate it. (grep -v)

But grep does not let you do a replace. And On the negation of a
regex.
Which programs would , and how?


Thanks. Sorry if this is not the appropriate newsgroup. If it is not,
then please let me know which is, and I will post it there.



..
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