Yeah, sorry for changing the post around. I thought I was replying to myself when in fact I was editing the original post.

Anyhow, here's a more concrete example:

@keywordList = ('john', 'john.smith', 'john.smith@mail.com');
$combinedExpression = combine(@keywordList);
# The combined expression looks something like this:
# (john(?:\.smith(?:\@mail\.com)?)?)
$searchText = "john's username is john.smith and his email address is 
+john.smith@mail.com";
while $searchText =~ /$combinedExpression/g {
   print "$1\n";
}
[download]

For this example, I expect to get these results:

john
john
john.smith
john
john.smith
john.smith@mail.com

Essentially, for every occurrence of every one of my keywords, I need to get a result, even if those keywords occur within other keywords in the input text.

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