Thanks, to the nice replays.

It is correct, that other scripts can open this special filename while the other process had found it as 'not there'.
But in the question, was nothing from multiple uses in the same time. I thought the author of this question (matth) wants to run his script often, without hardcoding the output filename.
The string, which you add to the filename, can be chosen from the md5 checksum of the content you want to paste ...or the a timepoint in msec...or what ever.
My reply only shows another 'way', when you don't want to use File::Temp.

Please be aware that File::Temp can cause problems with the network file system (nfs).