Occasionally, people lament that Perl has no switch/case statement like C. Perl6 has given/when, which goes several steps beyond the simple switch by handling arbitrary conditions, rather than simple equivalence.

So what does it buy you over if-else? Not a lot, in my experience. You can save some keystrokes by not retyping what you're matching against, and sometimes the ability to control whether things "fall through" -- matching multiple cases -- can come in handy.

Of course, we are not entirely without alternatives in Perl5. For simple multi-candidate equality testing without defaulting or fall-through, you can use a hash: 

my $consider = 'foo';
${{
    bar => sub { print "Barred!\n" },
    foo => sub { print "Fooed for thought...\n" }
}}{$consider}();

[download]
Grep is a natural tool for multi-way matching, and you can set it up to do fall-through and defaulting, though you do have to work at it: 
{
  my $continue = 1;
  $_->[1]() for grep {
    my ($cond, $then, $break)=@$_;
    local $_='boz'; # This is your given
    $continue and
    $cond->() and do { $continue = !defined $break; 1}
  }
  [sub {/z/}, sub { print "Hi!\n" }],
  [sub {/o/}, sub { print "Oh!\n" }, 'break'],
  [sub {1},   sub { print "This is the default\n" }]
  ;
}

[download]
Clearly you could encapsulate this in a function that takes your given and the list of condition-then(-break) sub pairs/triplets.

Still not pretty enough? Then maybe I can interest you in something that looks a lot like Perl6's given (even though I think it should have been called "consider" for better reading): 

{
  my $continue = 1;

  sub given ($$) {
    local $_ = shift;
    my $next = shift;
    my ($cond, $then);
    while ($next) {
      ($cond, $then, $next) = @$next;
      $then->() if $cond->() and $then;
      $continue or last;
    }
  }

  sub when (&$)  { [$_[0], @{$_[1]}] }
  sub then (&;$) { [@_] }
  sub default(&) { [@_] }
  sub done() { $continue = 0 }
  sub isit ($$)  { my @args=@_; [sub { $_ eq $args[0] }, @{$args[1]}] 
+}
}

given 'baz',
  isit 'baz', then { print "String match!\n" }
  when {/z/}  then { print "Hi!\n" }
  when {/o/}  then { print "Oh!\n"; done }
  default { print "This is the default\n" }
;

[download]
Given can only consider a scalar, but otherwise it's pretty comparable to the Perl6 critter, eh?

Update: added isit sub, to provide implicit eq check against $_. Writing when {$_ eq 'something'} for a lot of cases would get pretty old.

Caution: Contents may have been coded under pressure.

In reply to Switch/case (given/when) in Perl5 by Roy Johnson

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.