perl 沒有提供 switch 控制結構功能，下列方式可以使 perl 有 switch 控制結構的功能。
方法 1：使用 LABEL
方法 2：使用 feature module
方法 3：使用 Switch module
如果判斷條件需要重複動作，則須加 next ：
或使用 fall-through 模式：
方法 1：使用 LABEL
SWITCH: {
if (/^abc/) { $abc = 1; last SWITCH; }
if (/^def/) { $def = 1; last SWITCH; }
if (/^xyz/) { $xyz = 1; last SWITCH; }
$nothing = 1;
}
SWITCH: {
$abc = 1, last SWITCH if /^abc/;
$def = 1, last SWITCH if /^def/;
$xyz = 1, last SWITCH if /^xyz/;
$nothing = 1;
}
SWITCH: {
/^abc/ && do { $abc = 1; last SWITCH; }
/^def/ && do { $def = 1; last SWITCH; }
/^xyz/ && do { $xyz = 1; last SWITCH; }
$nothing = 1;
}
方法 2：使用 feature module
use feature "switch";
given($_) {
when (/^abc/) { $abc = 1; }
when (/^def/) { $def = 1; }
when (/^xyz/) { $xyz = 1; }
default { $nothing = 1; }
}
方法 3：使用 Switch module
use Switch;
switch ($value) {
case 17 { print "number 17" }
case "snipe" { print "a snipe" }
case /[a-f]+/i { print "pattern matched" }
case [1..10,42] { print "in the list" }
case (@array) { print "in the array" }
case (%hash) { print "in the hash" }
else { print "no case applies" }
}
如果判斷條件需要重複動作，則須加 next ：
%traits = (pride => 2, sloth => 3, hope => 14);
switch (%traits) {
case "impatience" { print "Hurry up!\n"; next }
case ["laziness","sloth"] { print "Maybe tomorrow!\n"; next }
case ["hubris","pride"] { print "Mine's best!\n"; next }
case ["greed","cupidity","avarice"] { print "More more more!"; next }
}
或使用 fall-through 模式：
use Switch 'fallthrough';
%traits = (pride => 2, sloth => 3, hope => 14);
switch (%traits) {
case "impatience" { print "Hurry up!\n" }
case ["laziness","sloth"] { print "Maybe tomorrow!\n" }
case ["hubris","pride"] { print "Mine's best!\n" }
case ["greed","cupidity","avarice"] { print "More more more!" }
}
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