Using a hash for this is very handy.

my %function = (
    set => \&set,
    add => \&add,
    mul => \&mul
);

# later:

if (exists $function{ $command } ) {
    $function{command}->($register,$param);
}
else {
    die "No such function: ($command)";
}
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Cheers,
Ovid

Looking for work. Here's my resume. Will work for food (plus salary).
New address of my CGI Course.