If you declare your subroutine with a function prototype specifying each argument as \% or \@, then your method will automatically get a reference to the hashes/arrays passed to it, without the person calling the function/method/subroutine needing to do anything special.

Note that, like all prototypes, this doesn't work when calling the subroutine using & or as a method.

See the 'Prototypes' section of perlsub for more details, or this node for a good example.

You can create a reference by simply prefixing a variable with \ like so:

processarrays(\@array1, \@array2);
processhashes(\%hash1, \%hash2);
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$sub processarrays{
   my($a1, $a2) = @_;
   foreach(@$a1){ # dereferences $a1
      print $_;
   }
   for($i=0; $i<@$a2; $i++){
       print $a2->[$i];  #get at a particular index within array
   }
}
sub processhashes{
   my($h1,$h2)=@_;
   foreach my $key(keys %$h1){ #derefences $h1;
      print $h1->{$key};  #lookup based on $key
   }
}
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