In other words, would it be possible to define a string and feed that into unpack, then define another string and feed it into the second part of join?

You'd have to explain that a little better, but someting like this might be close depending where/how you want to obtain those strings, The following would take comma separated arguments to construct the unpack template and field ordering: 

perl 
-e"BEGIN{$T=join'',map{qq[A$_ ]}split',',shift;@F=split',',shift}"  
-ple"$_ = join'',(unpack $T,$_)[@F]" 
"10,4,6,6" "2,1,0,3" infile >outfile

[download]

But note I've had to split the "one-liner" over several lines for posting. Once they start getting this long, writing a proper script is more convenient if you are going to reuse it.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re^3: Seeking an Enlightened Path (Parsing, Translating, Translocating) by BrowserUk
in thread Seeking an Enlightened Path (Parsing, Translating, Translocating) by nanotasher

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.