sub example { # Expects argument data that is a single value
      my %p = (@_); #
      return if $p{required} && !$p{data};
      Do stuff that references $p{data}...
      return 1; # OK
}


my $value  = 10;
if ( example(data=>$value, minval=>5, maxval=>10){
    print "$value is OK!\n";
}else{
    die "$value is naughty!";
}

Now let's say I want to extended it to take multiple values

I thought the easiest way would be to do this.

sub example { 
      my %p = (@_); #
      my @data = UNIVERSAL::isa($p{data},'ARRAY') ? @{$p{data}} : ($p{data});
      foreach $p{data} (@data){
        return if $p{required} && !$p{data};
        Do stuff that references $p{data}...
      }
      return 1; # OK

}