Assuming you don't want any linebreaks or whitespace at the end of the field, why not just:

$field =~ s/\s+$//;
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For linebreaks in the middle of the text, and coming from different machines, this works for me:

if ($field =~ m/\r/) { 
    $field =~ s/\n//g;
    $field =~ s/\r/<br>/g;
}
elsif ($field =~ m/\n/) { 
    $field =~ s/\n/<br>/g;
}
[download]