In case $data is empty, 

unless ( syswrite( $pc, $data ) == length $data ) {
    # ...
}

[download]

Or maybe just 

unless ( defined syswrite( $pc, $data ) ) {
    # ...
}

[download]

(Should it be considered an error if syswrite writes some number of bytes different from the length of the string you give it?)

In reply to Re^2: capturing syswrite failures by kyle
in thread capturing syswrite failures by Brad.Walker

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