Think of the c compiler doing something like this:
sub CompileSwitch{
my %hash;
my @commands;
my $command = 0;
my $mydefault;
while (@_) {
my $case = shift;
my $code = shift;
if ($case eq "default") {
$mydefault = $code;
last;
}
$hash{$case} = $command++;
push @commands,$code;
}
return sub{
my $case = shift;
my $i = $hash{$case};
if (defined $i) {
# fall through , a C switch doesn't test following cases it
# just goes to the end or till it hits a break
for (;$i<@commands;$i++) {
# execute code
&{$commands[$i]}
}
}
elsif (defined $mydefault) {
&$mydefault;
}
}
}
my $switch = CompileSwitch(
'a'=>sub { print "a"},
'b'=>sub { print "b"},
'c'=>sub { print "c"; last},
'x'=>sub { print "x"},
'y'=>sub { print "y"},
'z'=>sub { print "z"},
'default'=>sub { print "unknown case"}
);
foreach (qw(a b c d e f x y z)) {
print "testing $_\n";
$switch->($_);
print "\n";
}
__OUTPUT__
testing a
abc
testing b
bc
testing c
c
testing d
unknown case
testing e
unknown case
testing f
unknown case
testing x
xyz
testing y
yz
testing z
z
