Slice of a hash of hashes

davemabe has asked for the wisdom of the Perl Monks concerning the following question:

I want to do this:

open (FILE,$file); # $file is a |-delimited file
my @header = ('h1','h2','h3'); # I already know the headings
my %values; # make a hash of hashes to remember the values

while (<FILE>) {
  chomp;
  my @columns = split /\|/;
  my $unique = $columns[1]; # h2 is the unique identifier
  @values{$unique}{@header} = @values;
}
[download]

... but I get a Can't use subscript on hash slice error. Is there a good way to do this without doing it "manually?" I can think of several ugly ways to do it. I know @values{@header} = @columns; works, so I assume it will work for a more complex hash.

Dave

Comment on Slice of a hash of hashes Select or Download Code

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Re: Slice of a hash of hashes by chipmunk (Parson) on Jan 08, 2001 at 21:41 UTC
It looks like you're dereferencing things in the wrong order. Try this: `@{ $values{$unique} }{@header} = @values;` `$values{$unique}` is a hash reference; `$values{$unique}{$header}` is a single element from the referenced hash; and `@{$values{$unique}}{@header}` is a hash slice on the referenced hash.	[reply] [d/l] [select]
Re: Slice of a hash of hashes by davorg (Chancellor) on Jan 08, 2001 at 21:46 UTC
This seems to do the job: `#!/usr/bin/perl -w use strict; my @header = ('h1','h2','h3'); # I already know the headings my %values; # make a hash of hashes to remember the values while (<DATA>) { chomp; my @columns = split /\\|/; my $unique = $columns[1]; # h2 is the unique identifier @{$values{$unique}}{@header} = @columns; } __END__ val1\|one\|1 val2\|two\|2 val3\|three\|3` [download] I assume that the `@values` was a typo and have changed it to `@columns`. -- <http://www.dave.org.uk> "Perl makes the fun jobs fun and the boring jobs bearable" - me	[reply] [d/l]