Here's some more unrequested advice:

for (1..$num) {
  open my $fh, '>', sprintf "temp%02d",$_; # temp01, temp02, etc.
  ...
}
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Consider doing this if you plan to have more than 9 temp files and you want to keep them in numerical order. %02d will pad an integer with leading zeroes until it's two digits long. For more information, consult perldoc -f sprintf. You can even use a base-10 logarithm before the loop to figure out how many leading zeroes you would need, then insert that number into your format string.

EDIT: forgot that $_ is not implied with sprintf