open expects a file name/path, not a wildcard or regular expression (think of it this way: What should it do in case more than one file would match? Open several files to one handle?).

Use glob to expand a wildcard expression (the single unknown digit would be [0-9]), and then open one of the matching file names.

glob() works great! thank you

By the way, escaping _ and - is unnecessary in string literals, in regex patterns and in glob patterns. Escaping them is just visually confusing.

Also, by simply appending : $! to your error message, you make it far more useful.

Thank you for the hints. I escaped _ because of the scalars containing _ in their names. if I use my @cachefiles = glob("/home/cache/*_$scalar_1_2"); it does not recognize $scalar_1 I'd have to write my @cachefiles = glob("/home/cache/*_$scalar_1\_2");

"...${scalar}_..."
[download]

would also do. The curly method also works where a slash wouldn't.

"...${abc}def..."
[download]