When it is true that you can almost use anything as delimiter, you have to be aware that "'" behaves differently, as it will prevent $1 being interpreted. 
s'(^\d+[.]\s.+)'<h1>$1</h1>'g;

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does NOT work as you exepcted, unless you use /e modifier.

In reply to Re: s!!! vs. s/// by pg
in thread s!!! vs. s/// by imlou

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