in reply to Re^2: Extract length sum from columns and print pattern into another file
in thread Extract length sum from columns and print pattern into another file

poj has shown you how to open a normal file. The previous code that used DATA is using the special filehandle DATA, which reads from beyond the __DATA__ marker, as if it were a separate, already-opened file. For more on the __DATA__ special literal, and the automatic DATA filehandle, see https://perldoc.perl.org/perldata.html#Special-Literals

edit: clarify

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