One slight nit: if the file size isn't a multiple of the buffer size, the final seek will seek back too far and corrupt the final block. 
while(sysread $fh, $_, $BUFSIZE ) {
      tr[123][123];
      sysseek $fh, -length(), 1;
      syswrite $fh, $_;
}

[download]
(untested).

Dave.

In reply to Re^2: Muy Large File by dave_the_m
in thread Muy Large File by BuddhaLovesPerl

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