----- mainscript.pl
use SecondScript qw ( modify_array );

my @array = ('one', 'two', 3);

my @modified_array = @{modify_array(\@array)};
----- END

----- SecondScript.pm
package SecondScript;

use strict;
use warnings;

require Exporter;

use vars qw(@ISA @EXPORT_OK);

@ISA = qw(Exporter);
@EXPORT_OK = qw(modify_array);

sub modify_array {
  my @array = @{(shift)};
  # make your modifications here
  return \@array;
}
----- END