G'day paul-s-,

Welcome to the monastery.

This solution, which requires Perl 5.10.0, will skip your Windows files and allow you to process the Unix files.

Given these files:

$ cat -vet pm_1070943_CRLF.txt
text^M$

$ cat -vet pm_1070943_LF.txt
text$
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[Note: "cat -vet" shows special characters in files: '^M' = carriage return; '$' = newline]

This script:

#!/usr/bin/env perl

use 5.010;
use strict;
use warnings;
use autodie;

for my $file (qw{pm_1070943_CRLF.txt pm_1070943_LF.txt}) {
    open my $fh, '<', $file;
    my $first_line = <$fh>;
    $first_line =~ /(\R)\z/;

    if ($1 eq "\x0D\x0A") {
        say "Skipping: $file";
    }
    else {
        say "Processing: $file";
    }
}
[download]

[Note: '\R' is described in "perlrebackslash: Misc"]

Produces this output:

Skipping: pm_1070943_CRLF.txt
Processing: pm_1070943_LF.txt
[download]