By default, Perl passes arguments by reference (or, technically, by alias). If you modify the elements of the @_, you will modify the variables that were passed in:

use strict;
use warnings;

sub modify_args {
  $_[0] = 'new-value';
}

my ($one, $two) = qw(cat dog);

modify_args($one, $two);

print "$one $two\n";
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Of course, you can also pass references instead of the variables themselves, and then unload @_ in the usual way so that you don't have to work with that undescriptively-named array. Or you can take references to the elements of the array:

sub modify_args1 {
  my ($argref1, $argref2) = \(@_[0..$#_]);
  $$argref1 = 'new value';
}
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