open my $fh, "<$file";
read $fh, my $data, -s $file;
my $transposed = '';

for ( my $l=length( $data ), my $i = 0; $i < $l; $i++ ) {
    my $chr = substr( $data, $i, 1 );
    my $ascii = ord( $chr );

    if ( $chr eq "\n" ) {
        $transposed .= $chr;
        next;
    }

    if ( ( $ascii < 32 ) or ( $ascii > 126 ) ) {
        # e.g. ctrlc becomes '\003'
        $transposed .= '\' . Lzro3( $ascii );
    }
    else {
        # escape backslash to make it easier to translate back again
        ( $chr eq '\' ) and $chr .= '\';
        $transposed .= $chr;
    }
}

sub Lzro3 {
    my $n = shift;
    ( $n < 10 ) and return '00' . $n;
    ( $n < 100 ) and return '0' . $n;
    return $n;
}