#!/usr/bin/perl -w
use strict;

my @array = (1..10);

print join(", ",@array),"\n";

sillyfunc(\@array);

print join(", ",@array),"\n";

sub sillyfunc{
     my $aref = shift;
     # multiply each element by itself.
     $_ *= $_ foreach @{$aref};
}
__END__

Even if you don't want to modify the original data, 
refs are used to avoid flattening.
@array1=(1,2,3); @array2=('a','b','c');
(@array1,@array2) flattened would equal (1,2,3,a,b,c); 
What elements belong to which array?