IMO the eval version is much clearer than anything involving pack/unpack could be. 
$ perldoc -f eval|wc -c
6610
$ perldoc -f pack|wc -c
23377

[download]
That's right, pack's documentation is over three and a half times longer, and is littered with platform dependencies, arbitrary one character magic values, and special cases. It's so complicated that it needs a 51,000 character tutorial to go with it.

And your use of << is buggy. On a 32 bit machine the results are undefined. On a 64-bit machine you lose the obvious relationship between the /bits and the netmask (you'll have too many 1 bits) although the results will still be correct as the extra 1s will be ANDed with 0 and so thrown away later.

In reply to Re^2: String eval is cool by DrHyde
in thread String eval is cool by DrHyde

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.