On the contrary - multiple implementations happen if there is a specification. These languages tend to fragment if the spec is too big or if there is no good co

On the contrary - multiple implementations happen if there is a specification. These languages tend to fragment if the spec is too big or if there is no good compatibility testsuite. On the other hand, languages like Perl make it impossible to create another implementation because the original implementation is the spec. That requires any other implementation to follow the original's behavior in every weird corner case that has been observed or might just be spotted in two years from now. Reimplementers will never be done and be tightly tied to the original project, which would make the whole endeavour pointless for most intents and purposes.