You could use a negative look-ahead assertion (see perlre) $sample =~ s{(img src=")(?!http)}{$1$http}g; which gives the following output: 
<img src="http://domain.com/pics/local.jpg" alt="" />
<img src="http://remote.com/pics/remote.jpg" />
more confusion, just in case: 3:00pm 12/12/12
other urls <a href="http://fake.com">
http://fake.com</a>

[download]

But it's probably fraught with danger.

In reply to Re: Find and replace with regex by FunkyMonk
in thread Find and replace with regex by JayBee

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