+ if(length($isbn) <=10){
+ $len = 5;
+ $len = 1 if ( substr( $isbn, 0, 1 ) <= 7 );
+ $len = 2 if ( substr( $isbn, 0, 2 ) <= 94 );
+ $len = 3 if ( substr( $isbn, 0, 3 ) <= 995 );
+ $len = 4 if ( substr( $isbn, 0, 4 ) <= 9989 );
+
+ my $x = substr( $isbn, $len );
+ my $seg2;
+
+ if ( substr( $x, 0, 2 ) <= 19 ) {
+ $seg2 = substr( $x, 0, 2 );
+ }
+ elsif ( substr( $x, 0, 3 ) <= 699 ) {
+ $seg2 = substr( $x, 0, 3 );
+ }
+ elsif ( substr( $x, 0, 4 ) <= 8399 ) {
+ $seg2 = substr( $x, 0, 4 );
+ }
+ elsif ( substr( $x, 0, 5 ) <= 89999 ) {
+ $seg2 = substr( $x, 0, 5 );
+ }
+ elsif ( substr( $x, 0, 6 ) <= 9499999 ) {
+ $seg2 = substr( $x, 0, 6 );
+ }
+ else {
+ $seg2 = substr( $x, 0, 7 );
+ }