While Tom Christiansen was working on the Cookbook, he and I
were once musing how to write a regex that matches strings
that doesn't contain a certain pattern. We came up with:
/^(?:(?!pattern).)*$/s;
which is pretty straight forward if you realize how regular
expressions are matched.
For your problem, this leads to:
s/^((?:(?!toto).)*?)foo/${1}bar/s;
And if Japhy's new \K assertions gets accepted,
you will be able to write it as:
s/^((?:(?!toto).)*?)\Kfoo/bar/s;
Abigail
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