Obtain a switch/case behaviour in Perl 5

by

If you are using Perl 5.10 you have given/when which is a switch statement (note, it can do more than compare with regexes, read the linked docs to see its full potential):

#or any of the dozen other ways to tell 5.10 to use its new features
use feature qw/switch/; 

given($string) {
    when (/^abc/) { $abc     = 1; }
    when (/^def/) { $def     = 1; }
    when (/^xyz/) { $xyz     = 1; }
    default       { $nothing = 1; }
}

If you are using Perl 5.8 or earlier you must make do with if/elsif/else statements:

if    ($string =~ /^abc/) { $abc     = 1; }
elsif ($string =~ /^def/) { $def     = 1; }
elsif ($string =~ /^zyz/) { $xyz     = 1; }
else                      { $nothing = 1; }

or nested condition operators (?:):

$string =~ /^abc/ ? $abc     = 1  :
$string =~ /^def/ ? $def     = 1  :
$string =~ /^xyz/ ? $xyz     = 1  :
                    $nothing = 1;

There is a module in Core Perl (Switch) that gives you fake switch statements via source filters, but it is my understanding that it is fragile:

use Switch;

switch ($string) {
    case /^abc/ {
    case /^abc/ { $abc     = 1 }
    case /^def/ { $def     = 1 }
    case /^xyz/ { $xyz     = 1 } 
    else        { $nothing = 1 }
}

or the alternate syntax

use Switch 'Perl6';

given ($string) {  
    when /^abc/ { $abc     = 1; }
    when /^def/ { $def     = 1; }
    when /^xyz/ { $xyz     = 1; }
    default     { $nothing = 1; }
}

More Related Contents:

  1. Why is the Switch module deprecated in Perl?
  2. how to check if a number is whole number or contains a decimal
  3. How can i do this in perl, shortcut truthtable [closed]
  4. How to retrieve the values of required keys in Perl [closed]
  5. Perl: Meaning of double squared brackets after a string?
  6. What does this HTML::Parser() code do in Perl? [closed]
  7. Why use strict and warnings?
  8. Why does modern Perl avoid UTF-8 by default?
  9. Why is three-argument open calls with autovivified filehandles a Perl best practice?
  10. How can I install a CPAN module into a local directory?
  11. What’s the difference between Perl’s backticks, system, and exec?
  12. Perl daemonize with child daemons
  13. How can I parse dates and convert time zones in Perl?
  14. Which one is good practice, a lexical filehandle or a typeglob?
  15. How do I tell if a variable has a numeric value in Perl?
  16. Using perl’s `system`
  17. What’s the best way to open and read a file in Perl?
  18. Perl memory usage profiling and leak detection?
  19. How should I use the “my” keyword in Perl?
  20. Global symbol requires explicit package name
  21. How do I include functions from another file in my Perl script?
  22. Use of ‘use utf8;’ gives me ‘Wide character in print’
  23. How can I interact with ClearCase from Perl?
  24. What reasons are there to prefer glob over readdir (or vice-versa) in Perl?
  25. How do I convert a date/time to epoch time (unix time/seconds since 1970) in Perl?
  26. What does =~ do in Perl? [closed]
  27. How to convert letters with accents, umlauts, etc to their ASCII counterparts in Perl?
  28. What does shift() do in Perl?
  29. How can I extract text from a PDF file in Perl?
  30. How do I retrieve the terminal width in Perl?

Leave a Comment