sprintf takes the same arguments as printf (except filehandle) but returns the formatted string instead of printing it.

In fact,

printf FH "%s ==> %i", $string, $int;
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Is equivalent to:

print FH sprintf("%s ==> %i", $string, $int);
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So you could easily use

mkdir(sprintf($format, @stuff));
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Which would be much more elegant than writing to a file, then reading it back.