Or you could use an array of hashes.

#hoaMessing.pl
use strict;
use warnings;
use Data::Dumper;

my $file = '3column.file';
#contains 
#a b c
#d e f
#g h i
my $i=0;
open (INPUT, "<$file") or die "Could not open $file: $!";
my (%left_hash,%middle_hash,%right_hash);
my $line_number = 0;
my @lines;
while    (<INPUT>) {
    my %line;
    ($line{left},$line{middle},$line{right}) = split (/\s+/, $_);
    $line{line_number} = $line_number;

    push @lines,\%line;
    $line_number++;
}

print Dumper(\@lines);
#prints
#$VAR1 = [
#          {
#            'middle' => 'b',
#            'left' => 'a',
#            'right' => 'c',
#            'line_number' => 0
#          },
#          {
#            'middle' => 'e',
#            'left' => 'd',
#            'right' => 'f',
#            'line_number' => 1
#          },
#          {
#            'middle' => 'h',
#            'left' => 'g',
#            'right' => 'i',
#            'line_number' => 2
#          }
#        ];
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