As stated before sysopen comes with more precision than open.

sysopen helps avoiding race-conditions.

Consider the following snippet:

if (-e $file) {
        open(FH,">","$file") or die $!;
}
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It's a two step process:

1. File test
2. open

sysopen needs only one step (kind a simplistic, but you should get the message).

use Fcntl;

sysopen(FH, $file, O_WRONLY|O_TRUNC|O_CREAT, 0600)
        or die $!;
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HTH,
Thomas