I'm sure Tie::CSV_file is a fine module, but you might also give Parse::CSV a spin. Here's some cutting and pasting of some code I wrote recently.

use Parse::CSV;

# Define the names of our csv fields
#
my $csv_fields = [
                'CoordinatorID',
                'CompanyName',
                'FirstName',
                'LastName',
                'City',
                'State',
                'csgaccount',
                'Username',
                'DomainName'
                ];

# Populate these hashrefs with data for comparison with the
# list of names.
#
my $provisioned     = fetch_csv_accounts({ filename => $opts->{prov},
                                           fields   => $csv_fields });

# {{{ sub fetch_csv_accounts
#
sub fetch_csv_accounts {

    my $args = shift;

    die "No field names provided...\n" unless defined $args->{fields};
    die "No filename provided...\n"    unless defined $args->{filename
+};

    # Default the keyfield to Username if nothing
    # is passed to this sub.
    #
    my $keyfield =   $args->{keyfield}
                   ? $args->{keyfield}
                   : 'Username';

    #
    # Create a Parse::CSV object for easy csv iteration
    #
    my $prov_csv = Parse::CSV->new( file   => $args->{filename},
                                    fields => $args->{fields}, );

    die "Error: " . $prov_csv->errstr . "\n" if $prov_csv->errstr;

    # Loop through each row of the csv file and populate the
    # hashref.  The resulting hashref will look like:
    #
    #   Username1     -> CoordinatorID
    #                 -> CompanyName
    #                 -> FirstName
    #                 -> Lastname
    #                 -> City
    #                 -> State
    #                 -> csgaccount
    #                 -> Username
    #                 -> DomainName
    #   Username2     -> CoordinatorID
    #                 -> CompanyName
    #                 ... etc ...

   my $return_hash = {};

    while ( my $row = $prov_csv->fetch ) {
        foreach ( keys %{$row} ) {
            $return_hash->{ $row->{$keyfield} }->{$_} = $row->{$_};
        }
    }

    return $return_hash;


} # }}}
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