From the perldocs for File::Temp:
Trailing `X' characters are replaced with random letters to generate the filename. At least four `X' characters must be present at the end of the template.
And the relevant code from the module: 
  # Do it using substr - no reason to use a pattern match since
  # we know where we are looking and what we are looking for

  if (substr($template, $start - MINX + 1, MINX) ne 'X' x MINX) {
    ${$options{ErrStr}} = "The template must contain at least ".
      MINX . " 'X' characters\n";
    return ();
  }

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In reply to Re: tempdir with template fails by imp
in thread tempdir with template fails by Skeeve

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