Actually, I wouldn't recommend quotemeta in tasks like this. It's seldom or never the case that regex-magic characters will be needed as literals in the patterns being conjoined, but even if this comes up, it can still be better to escape them explicitly as needed (when assigning to the array), and allow some strings to use regex-magic where appropriate:

my @fields = ('From: ', 'Subject: ', 'Thread-\w+: ', 'What-if-there\'s
+-a-qmark\?');

# 3rd element matches "Thread-Topic: ", "Thread-Index: ", etc.
[download]

Obviously, in a context where strings are coming from a potentially tainted source (i.e. not from the source code itself), one must weigh the relative risk/benefit and coding-effort/ease-of-use trade-offs of prohibiting vs. allowing (and taint-checking) regex metacharacters in applications like this.