The inherent weakness in your query is that you are asking for a Perl equivalent to a basic 'switch' idiom, when Perl doesn't provide a 'switch' construct.

You are asking about Duff's Device ..... which, as I remember, was invented to save a couple dozen machine instructions. My understanding is that Duff's Device is mostly viewed as poor programming, since saving a few dozen machine cycles at 3 GHz is less important than leading to quick and clear reader understanding of the code. On the other hand, I can imagine programmers dealing with highly-efficient code, such as embedded programmers, might accept Duff as an easily recognized idiom.

So the next question is, without a switch statement, how would we implement Duff?

We've had one suggestion, using substr(), very closely related to the details of this question.

More generally, you might consider re-framing the conditionals:

for my $val ( $var ) {
    print "a" if ( $val >= 10 );
    print "b" if ( $val >= 9 );
    print "c" if ( $val >= 8 );
    print "d" if ( $val >= 7 );
    print "e" if ( $val >= 6 );
    print "f" if ( $val >= 5 );
    print "g" if ( $val >= 4 );
    print "h" if ( $val >= 3 );
    print "i" if ( $val >= 2 );
    print "j" if ( $val >= 1 );
}

[download]

So, yes, it can be achieved, but you need to think somewhat differently.

--
TTTATCGGTCGTTATATAGATGTTTGCA

In reply to Re: fall through switch/case in perl by TomDLux
in thread fall through switch/case in perl by ykar

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.