NAME Switcheroo - yet another switch statement for Perl SYNOPSIS my $day_type; switch ($day) { case 0, 6: $day_type = "weekend"; default: $day_type = "weekday"; } STATUS Experimental. No backwards compatibility between releases is guaranteed. Both the surface syntax and the internals of the module are liable to change at my whim. DESCRIPTION This module provides Perl with a switch statement. It's more reliable than the Switch module (which is broken on recent versions of Perl anyway), less confusing than `use feature 'switch'`, and more powerful than Switch::Plain (though Switch::Plain is significantly faster). Switcheroo uses the Perl keyword API, which was introduced in Perl 5.14, so this module does not work on older releases of Perl. The basic grammar of the switch statement is as follows: switch ( TEST ) { case EXPR1: STATEMENT1; case EXPR2: STATEMENT2; default: STATEMENT3; } TEST is evaluated in scalar context. Each expression EXPR1, EXPR2, etc is evaluated in list context. If TEST matches any of the expression, then the statement following it is executed. Matching is performed by match::simple, which is a simplified version of the Perl smart match operator. If no match is successful, then the `default` statement is executed. `switch` is whole statement, so does not need to be followed by a semicolon. Within the switch block, $_ is a read-only alias to the TEST value. That's the basics taken care of, but there are several variations... Implicit test If the test is omitted, then $_ is tested: my $day_type; $_ = $day; switch { case 0, 6: $day_type = "weekend"; default: $day_type = "weekday"; } Expression blocks If `case` is followed by a `{` character, this is *not* interpreted as the start of an anonymous hashref, but as a block. Matching via match::simple is not attempted; instead the block is evaluated as a boolean. switch ($number) { case 0: say "zero"; case { $_ % 2 }: say "an odd number"; default: say "an even number"; } Regexp Expressions If this module encounters: switch ($foo) { case /foo/: say "foo" } Don't worry; we know you meant `qr/foo/` and not `m/foo/`. Statement blocks If the first non-whitespace character is `{`, the statement is treated as a block rather than a single statement: switch ($number) { case 0: { say "zero"; } case { $_ % 2 }: { say "an odd number"; } default: { say "an even number"; } } Comparison expression Above I said that matching is performed by match::simple. That was a lie. match::simple is just the default. You can provide your own expression for matching: switch ($number) mode ($a > $b) { case 1000: say "greater than 1000"; case 100: say "greater than 100"; case 10: say "greater than 10"; case 1: say "greater than 1"; } $a is the TERM and $b is the EXPR. These are the same special package variables used by `sort` and by `reduce` from List::Util. Switch expressions Although `switch` acts as a full statement usually, it can be used as part of an expression if the keyword `do` appears before the block: my $day_type = switch ($day) do { case 0, 6: "weekend"; default: "weekday"; }; Fallthrough There's no fallthrough. `match($x, $y)` This module can also re-export the `match` function from match::simple, but not by default. use Switcheroo qw( match switch ); HINTS Switcheroo intentionally works nicely with Types::Standard and other Type::Tiny-based type libraries: use Switcheroo; use Types::Standard -types; switch ($value) { case Int: say "it's an integer"; case ArrayRef: say "it's an array ref"; case HashRef: say "it's a hash ref"; } It also plays well with Smart::Match: use Switcheroo; use Smart::Match qw( range at_least ); switch ($value) { case range(0, 10): say "small"; case range(11, 100): say "medium"; case at_least(101): say "large"; } This is all thanks to match::simple which respects the overloaded `~~` operator. CAVEATS Internally a lot of parts of code are passed around as coderefs, so certain things might not work how you'd expect inside `switch`: * `caller` * `return` * @_ BUGS Please report any bugs to . SEE ALSO "Switch Statements" in perlsyn, Switch, Switch::Plain. . AUTHOR Toby Inkster . COPYRIGHT AND LICENCE This software is copyright (c) 2013 by Toby Inkster. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. DISCLAIMER OF WARRANTIES THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.