To avoid using "real" files for demonstration purposes I used Perl's facility for using a string as a file by passing a reference to the string into the open. To open a real file instead you should:

open my $in, '<', $fileName or die "Unable to open $filename: $!";

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Please follow my advice and use strictures (use strict; use warnings; - see The strictures, according to Seuss), the three parameter form of open and lexical file handles (the 'my $in' bit in my sample code). These tips will save you time in the future!

If you open an output file ($out) before the loop in my sample code you can change the print to:

    printf $out $format, $key, @{$data{$key}}{@columnNames};

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to print to the output file instead of STDOUT. Note that for testing and sample code using STDOUT is often much more convenient!

True laziness is hard work

In reply to Re^4: Hash w/ multiple values + merging by GrandFather
in thread Hash w/ multiple values + merging by sophix

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