The problem is that what is or is not an IP address really depends on the file semantics, not just on what an IP address "looks like." A simple regex match for dotted-quad "IP addresses" in arbitrary text will give you false positives.

In the HTML source for one site I maintain, for example, such a regex would match the following:

        1.41.1.1
[download]

Is it an IP address? Nope, it's an RCS version number, and blindly assuming it's an IP address would be wrong at best and dangerous at worst.

That said,

        @ip_addrs = m/{regex to match IP}/g;
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will select only the "IP address" texts from $_ for whatever regex you choose, without the danger of relying on $1.