# Untested, but should work
use 5.6.0;

use strict;
use warnings;

package FieldStorage;

use Exporter;
our @ISA = qw(Exporter);

# Using @EXPORT instead of @EXPORT_OK because we want these definitely 
# in the caller's namespace. If we don't, use @EXPORT_OK.
our @EXPORT = qw(
    getFieldNames
    isRequired
);

my %Fields = (
    FOO => {
        Order => 0,
        Required => 1,
    },
    BAR => {
        Order => 1,
        Required => 0,
    },
....
);

sub getFieldNames {
    return sort { $a->{Order} <=> $b->{Order} } keys %Fields;
}

sub getFieldIndices {
    return map { $Fields{$_}{Order} } @_ || getFieldNames;
}

sub isRequired {
    my $field = shift;

    return undef unless exists $Fields{$field};

    return $Fields{$field}{Required};
}

1;

__END__

##</code><code>##

use FieldStorage;

# Some stuff here

my @fieldNames = grep { isRequired($_) } getFieldNames;
my @fieldIndices = getFieldIndices(@fieldNames);

my %records;
@records{@fieldNames} = (split(/\t/, $_))[@fieldIndices];