+ my @fields = $record->field($tag);
+ $tag_fields_count->{$tag} = scalar @fields;
+ }
+
+ my $tags_count;
+ foreach my $key ( keys %$tag_fields_count ) {
+ if ( $tag_fields_count->{$key} > 0 ) { # Having 0 of a field is ok
+ $tags_count //= $tag_fields_count->{$key}; # Start with the count from the first occurrence
+ return -1 if $tag_fields_count->{$key} != $tags_count; # All counts of various fields should be equal if they exist