#!/usr/bin/perl
use strict;

sub compare ($$) {
    my ($a,$b) = @_;
    my $ok = 0;

    for (my $i=0; $i < scalar(@{$a}); $i++) {
        if ( @{$a}[$i] eq @{$b}[$i] && @{$a}[$i] ne "_" ) { 
                #compatible...
                $ok=1;
        } elsif (@{$a}[$i] ne @{$b}[$i] && (@{$a}[$i] ne "_" && 
                 @{$b}[$i] ne "_") ) {
                # totally not compatible
                return 0;
        }
    }
    $ok;
}

my @a1 = qw(_ 8 _ _ 3 _ _ 1 9);
my @a2 = qw(2 _ 8 _ _ _ 7 _ _);
my @a3 = qw(4 8 _ _ _ _ _ 7 _);
my @a4 = qw(4 8 _ _ _ _ 7 _ _);

print ( "1: " . compare(\@a1, \@a2) ."\n" );
print ( "2: " . compare(\@a1, \@a3) ."\n" );
print ( "3: " . compare(\@a1, \@a4) ."\n" );