Create a switch or case statement

				
Briefly, there's no official case statement, because of the variety of tests 
possible in Perl (numeric comparison, string comparison, glob comparison, regexp 
matching, overloaded comparisons, ...). Larry couldn't decide how best to do 
this, so he left it out, even though it's been on the wish list since perl1. 
The general answer is to write a construct like this: 
for ($variable_to_test) {
if(/pat1/) { } # do something
elsif (/pat2/) { } # do something else
elsif (/pat3/) { } # do something else
else{ } # default
} 

Here's a simple example of a switch based on pattern matching, this time 
lined up in a way to make it look more like a switch statement. We'll do a 
multi-way conditional based on the type of reference stored in $whatchamacallit: 
SWITCH: for (ref $whatchamacallit) {

/^$/&& die "not a reference";

/SCALAR/&& do {
print_scalar($$ref);
last SWITCH;
};

/ARRAY/ && do {
print_array(@$ref);
last SWITCH;
};

/HASH/ && do {
print_hash(%$ref);
last SWITCH;
};

/CODE/ && do {
warn "can't print function ref";
last SWITCH;
};

# DEFAULT

warn "User defined type skipped";

}

See perlsyn/"Basic BLOCKs and Switch Statements" for many other 
examples in this style. 
Sometimes you should change the positions of the constant and the variable. 
For example, let's say you wanted to test which of many answers you were given, 
but in a case-insensitive way that also allows abbreviations. You can use the 
following technique if the strings all start with different characters, or if 
you want to arrange the matches so that one takes precedence over another, as 
"SEND" has precedence over "STOP" here: 
chomp($answer = <>);
if("SEND" =~ /^\Q$answer/i) { print "Action is send\n" }
elsif ("STOP" =~ /^\Q$answer/i) { print "Action is stop\n" }
elsif ("ABORT" =~ /^\Q$answer/i) { print "Action is abort\n" }
elsif ("LIST" =~ /^\Q$answer/i) { print "Action is list\n" }
elsif ("EDIT" =~ /^\Q$answer/i) { print "Action is edit\n" }

A totally different approach is to create a hash of function references. 
my %commands = (
"happy" => \&joy,
"sad", => \&sullen,
"done" => sub { die "See ya!" },
"mad"=> \&angry,
);

print "How are you? ";
chomp($string = <STDIN>);
if ($commands{$string}) {
$commands{$string}->();
} else {
print "No such command: $string\n";
}