It depends on what your requirements for validation are. If you only want a ten digit number,

my $data_in="ISBN 90-70002-34-5";
   $data_in=~ s/^ISBN//;
   $data_in=~ s/ /-/g;
   $data_in=~ s/-//g;
my @isbn=split('', $data_in);
my $count=scalar @isbn;
unless (($count eq 10) && (!($count=~ m/[a-z]/i))){
   warn "not enough digits in ISBN: $count instead of 10\n";
}
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Now, if you are checking against a database to validate, it depends on the format of the ISBN that is stored. If it's space or hyphen delimited you can:

# data from the database you are checking against
my $data_in="90 70002 34 5";
# inputed data
my $check_data="ISBN 90-70002-34-5";
   $check_data=~ s/^ISBN//;
   $check_data=~ s/-/ /g;
   $check_data=~ s/^ //;
unless (($data_in eq $check_data) && (!($count=~ m/[a-z]/i))){{
   die "failure: data in does not match db record\n";
}
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Of course it all depends on how you want to validate. If you have access to a database of ISBNs and you can validate GroupID, Publisher prefix, and so on then validate against it. Other wise, the best you can hope for is that it's just 10 digits.

-phill

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