Perl subroutine references and anonymous subroutines

Subroutines also have references, as well as anonymous subroutines. Suppose you already have an array, hash reference knowledge, so here is a brief introduction.

$ref_sub = \&mysub; # Subprogram reference, & symbol must be less
&{$ref_sub}(ARGS) # Release the subroutine reference, pass the parameter ARGS
&$ref_sub(ARGS) # Resolve subroutine reference
$ref_sub->(ARGS) # Resolve subroutine reference
$ref_sub->() # Pass null parameter

Sub {...}; # Define anonymous subroutine, no name after sub
$ref_sub = sub {...}; # Anonymous subroutine reference

With the subroutine reference, you can invoke the subroutine on demand.

For example:

sub java_learn {
    print "Learning Java now\n";
}
sub perl_learn {
    print "Learning Perl now\n";
}
sub python_learn {
    print "Learing Python now\n";
}

%sub_hash=(
    "javaer"   => \&java_learn,
    "perler"   => \&perl_learn,
    "pythoner" => \&python_learn,
);

while(my ($who,$sub)=each %sub_hash){
    print "$who is learning\n";
    $sub->();
}

Change to Anonymous subroutine:

$javaer = sub {
    print "Learning Java now\n";
};
$perler = sub {
    print "Learning Perl now\n";
};
$pythoner = sub {
    print "Learing Python now\n";
};

foreach (qw(javaer perler pythoner)){
    print "$_ is learning\n";
    $$_->();
}

Even, use the anonymous subroutine as part of the data structure:

%sub_hash = (
    "javaer" => sub {
        print "Learning Java now\n";
    },
    "perler" => sub {
        print "Learning Perl now\n";
    },
    "pythoner" => sub {
        print "Learning Python now\n";
    },
);

while( my($who,$sub)=each %sub_hash ){
    print "$who is learning\n";
    $sub->();
}

The maximum effect of subroutine references and anonymous subroutines may be for callback functions (callback), closures (closure). This topic is a bit big, see the next article.

Perl subroutine references and anonymous subroutines