I don't understand what you mean by shuffling based on first field, a random shuffle is a random shuffle. Anyhow, here is some code to help you get started (the code for the shuffle is the same as in the docs (ie. perldoc -q random):

use strict;
use warnings;

my @array = <DATA>;
fisher_yates_shuffle(\@array);
print @array;


sub fisher_yates_shuffle {
    my $deck = shift;  # $deck is a reference to an ar
    my $i = @$deck;
    while ($i--) {
        my $j = int rand ($i+1);
        @$deck[$i,$j] = @$deck[$j,$i];
    }
}

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[download]

use strict;
use warnings;
use Tie::File;
use List::Util qw(shuffle);

my @file;
tie @file, 'Tie::File', 'foo.dat' or die $!;
@file = shuffle(@file);
[download]

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

What do you mean by a shuffle 'based on the first field'? I'd think in terms of shuffling whole records, and a random ordering doesn't usually depend on values.

Given the file size you mention, slurping to an array and hitting it with Fisher-Yates sounds like the right way to do it. What goes wrong with your attempt?

After Compline,
Zaxo

Can you provide a small code snippet that you've tried already? I'm not sure what you mean by "shuffle the file based on the first field", and it's tough to guess what kind of output you want.