Think of the c compiler doing something like this: 
sub CompileSwitch{
  my %hash;
  my @commands;
  my $command = 0;
  my $mydefault;
  while (@_) {
    my $case = shift;
    my $code = shift;
    if ($case eq "default") {
      $mydefault = $code;
      last;
    }
    $hash{$case} = $command++;
    push @commands,$code;

  }
  return sub{
    my $case = shift;
    my $i = $hash{$case};
    if (defined $i) {
      # fall through , a C switch doesn't test following cases it
      # just goes to the end or till it hits a break
      for (;$i<@commands;$i++) {
    # execute code
    &{$commands[$i]}
      }
    }
    elsif (defined $mydefault) {
      &$mydefault;
    }
  }
}

my $switch = CompileSwitch(
               'a'=>sub { print "a"},
               'b'=>sub { print "b"},
               'c'=>sub { print "c"; last},
               'x'=>sub { print "x"},
               'y'=>sub { print "y"},
               'z'=>sub { print "z"},
               'default'=>sub { print "unknown case"}
);

foreach (qw(a b c d e f x y z)) {
  print "testing $_\n";
  $switch->($_);
  print "\n";
}

__OUTPUT__
testing a
abc
testing b
bc
testing c
c
testing d
unknown case
testing e
unknown case
testing f
unknown case
testing x
xyz
testing y
yz
testing z
z

[download]

In reply to Re: Re: Re: Re: Re: Perl Idioms Explained: && and || "Short Circuit" operators by fletcher_the_dog
in thread Perl Idioms Explained - && and || "Short Circuit" operators by davido

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.