use strict;
use warnings;
use 5.010;


sub do_stuff {
    foreach (1..5) {
        &dangerous($_);
        say "calculation in do_stuff(): ", $_ * 10;
        
    }
}

sub dangerous {
    $_ = shift;
    $_ *= 100;
    say "calculation in dangerous(): $_"
}

&do_stuff();

--output:--
calculation in dangerous(): 100
calculation in do_stuff(): 1000
calculation in dangerous(): 200
calculation in do_stuff(): 2000
calculation in dangerous(): 300
calculation in do_stuff(): 3000
calculation in dangerous(): 400
calculation in do_stuff(): 4000
calculation in dangerous(): 500
calculation in do_stuff(): 5000

##</code><code>##

sub do_stuff1 {
    local $_ = shift;
    chomp;
    say;
}