the perlop page says nothing about adding new records to a hash with ++
This commonly seen Perl idiom works due to Autovivification (the automatic creation of a variable reference when an undefined value is dereferenced). Autovivification is unique to Perl; in other languages you'd need to create the item as a separate operation before incrementing it.

In reply to Re^5: Filtering very large files using Tie::File by eyepopslikeamosquito
in thread Filtering very large files using Tie::File by elef

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