The two line version is perfect - concise and clearly readable. Nevertheless, just for the record:

@iparray = unpack ('C4', (gethostbyname $machine) || next );
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Note that || forces scalar context on gethostbyname, in which case the address is the sole return value, rendering the slice unnecessary. Take a look at perldoc -f gethostbyname, most of Perl's functions make useful distinctions between their calling contexts.

But since you're populating an array, I guess you're doing this in a loop. If this is the only thing in that loop, you might actually consider condensing this using map along these lines:

my @iparray =
    map defined() ? join('.', unpack 'C4', $_) : (),
    map scalar(gethostbyname $_),
    @machine;
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