#!/usr/bin/perl
# usage: $0 [-d "delimiter"] file
use strict;
use warnings;
my $delimiter = '\t';
if ( $ARGV[0] =~ /^\-(.)$/ ) {
    $_ = $ARGV[1];
    if ( /^\"(.*)\"$/ ) {
        $delimiter = $1;
        shift @ARGV; shift @ARGV;
    }
}
my $file = join( '', @ARGV );
my %seen = ();
open my $fh, "<$file" or die "$!: $file\n";
while( <$fh> ) {
    chomp;
    my @cols = split( /$delimiter/ );
    for ( my $col=0; $col <= $#cols; $col++ ) {
        Check ( \%seen, $col[$col], $., $col+1 );
    }
}
close $fh;

sub Check {
    my ( $sref, $col, $lno, $colno ) = @_;
    my $lc = Transform( $col );
    my $xref;
    if ( $xref = $sref -> { $lc } ) {
        ( $sref -> { $lc }{ $col } )
            or print "Column $colno, Line $lno: ($col) "
                   . "varies from "
                   . ( values %$xref );
    }
    else {
        $sref -> { $lc }{ $col } = "Column $colno, Line $lno: ($col)\n";
    }
}

sub Transform{
    my $lc = lc( shift());
    # example of an additional transformation...
    $lc =~ s/\s*//g;
    return $lc;
}