It means exactly what it says, its the same as Re^5: Combining 3 files, undef, a number, a string ... none of those things are an array reference

Ok, now I'm more confused than ever and chasing my tail in frustration. This is where I am with the code. Any helpful suggestions are appreciated.

#!/usr/bin/perl
#22/06/2011

#use strict;
use warnings;
use File::Slurp;
use Data::Dumper;
my @data;
my @col;
my $dataset;
my @fields;
#my %out;
my $Hashref;
my $fileCount;
my @out; 
my @results;

open INFILE, "<Primer-Rev1" or die $!;
open my $outfh, '>', "outputfile.txt" or die $!;

    for my $nr (1..2) {
     for my $line (read_file('Primer-For'.$nr)) {
      my @col = split(/\t/,$line);


      push @{$data[$nr - 1]->{shift(@col)}},\@col;
     }
    }


while (<INFILE>){

        @col = split(/\t+/, $_);
        chomp (@col);
         my ($header, $length, $tm, $sequence) = @col[0..3];

        # expecting file3 line in @col

        my @results = ( $col[1], $col[2] );

#print Dumper (\@results)
}

for my $dataset (@data) {
    my @out = push @{
    $data[ $fileCount ]->{
        shift @col
    }
},  \@col;



#print Dumper (\@data);
}

    @out = 
        sort {
            my $diff_a = $col[2] - $a->[1];
            $diff_a *= -1 if $diff_a < 0;
            my $diff_b = $col[2] - $b->[1];
            $diff_b *= -1 if $diff_b < 0;
            $diff_a <=> $diff_b;
          }   @out;

print Dumper (\@out);

    push @results, $out[0]->[2];

#print Dumper (\@results);
#}
[download]

Ok, now I'm more confused than ever and chasing my tail in frustration.

You still have

my @out = push @{
    $data[ $fileCount ]->{
...
[download]

Why?