use warnings;
use strict;
use diagnostics;

my $string = "";

add_i_to_string($string);

sub add_i_to_string {
    my ($string) = @_;
    my $new_string = $string . "i";
    add_am_to_string($new_string);
}

sub add_am_to_string {
    my ($string) = @_;
    my $new_string = $string . " am";
    add_ironman_to_string($new_string);
}

sub add_ironman_to_string {
    my ($string) = @_;
    my $new_string = $string . " ironman";
    string_print($new_string);
}

sub string_print {
    my ($string) = @_;
    print $string;
}

#prints "i am ironman"