$|=1 only sets autoflush on the currently selected filehandle, which is STDOUT, and won't solve the issue for the FIL handle.

Instead, he wants to

open(FIL,">>$myfil") || "Can't open $myfil: $! \n";
select((select(FIL), $|=1)[0]);
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or alternatively, and much easier on the eyes,

use IO::Handle;
open(FIL,">>$myfil") || "Can't open $myfil: $! \n";
FIL->autoflush();
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____________
Makeshifts last the longest.