undef $/;
$regel = <FH_input>
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All this does is read the entire contents of your input file into $regel in one fell swoop. It should still have the newlines in it that it had originally, and in any case how you do your input shouldn't have any impact on newlines that you explicitely insert in your output. I'd say that's not your problem. Maybe you should post the whole script here.

Maybe Notepad is part of the issue. What happens if you look at the file in another editor (UltraEdit or whatever, or even EDIT.COM) or pull up a command prompt and use the TYPE command to display it?

$;=sub{$/};@;=map{my($a,$b)=($_,$;);$;=sub{$a.$b->()}}
split//,".rekcah lreP rehtona tsuJ";$\=$ ;->();print$/
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