while <(inFile)> {
     my @record = split /\|/, $_;
     my %eslist = $record[3];
}
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A hash stores a key and a value so it doesn't make sense to assign an odd number of elements to a hash. Perhaps your code should look like:

my %eslist = ($record[3] => 1);
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---

True laziness is hard work

Okay, I need help! :) Here is my code so far. What I want to do is send all the unique values in %eslist to a text file. eslist has numbers in it ranging from 1 to 5 digits. I've tried variations on getting eslist into a uniqe file but none of them work so I'm not including them here because I think they are completely wrong and just confusing me. Thanks for any help or direction you can give me.


use strict;
use warnings;

my %eslist;

open(inFile, "< C:\\input.txt")
  || die "Unable to open file - $!\n";

open( OUTFILE, "> C:\\output.txt" )
  || die "Unable to open write file! - $!\n";

while(<inFile>) {
    my @record = split /\|/, $_;
    my $tn     = $record[0];
    my $err    = $record[1];
    my $ent    = $record[2];
    %eslist    = ($record[3] => 1);
    my $coid   = $record[4];

    
}
close inFile;
close OUTFILE;
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     my %eslist = $record[3];
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That code declares a hash variable (using my) and assigns a single scalar value to the hash. In the words of diagnostics

(W) You specified an odd number of elements to initialize a hash, 
which is odd, because hashes come in key/value pairs.
[download]

What is in $record[3]? What other data do you want to associate with $record[3]? If you show us a small sample of data, we could probably suggest how you might store the data in a hash.

Give perldata a quick read.

record[3] is a bunch of numbers. I'm trying to find all unique entries. From what I've read a hash is the best way to do this, but I'm having trouble understanding how to assign a key to the record[3] value. Is a key like a primary key in a database? Where it is essentially a arbitrary unique number used to refer to the entry?

OK, I think I see what you are trying to do, but a hash may not be what you want. A list might be better for your needs. List ex:

use List::MoreUtils qw(any);  #instead of using: 
                              #     "if (grep( m/whatever/, @list)){}"
                              #use: "if (any { m/whatever/} @list){}" 
                              #this exits on the first occurrence.

if (!any {m/^\Q$record[3]\E$} @esList){ 
   #the \Q\E guarantees that the value held in the $record[3] 
   #is not interpreted as a regular expression

    push (@esList = $record[3]);
}
### @esList is now a unique list of the values you want...
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But if you really want to use a hash, this is how you might do it:

my %esList = ();
$esList{$record[3]) = 1;

### then to recall all the found records:
foreach my $result {sort(keys(%esList))){
    print "found record: $result \n"; 
}
[download]

Also, if you're interested, I started a discussion recently about how to best implement multidimensional hashes, they have some unique characterictics that you might not expect when trying to extending principals of a one dimensional hash. But there are some very good references listed there. It can be found at: Best Multidimensional Hash Practices? Good luck...