The >filename is open for appending (perlfunc::open & perlopentut). If the file does not exist, it'll be created (and you need directory permissions for that - ofcourse you also need them to append anyway). Check if the user nobody can access the file you wish to open.
I suggest you use some I/O checking and use

open(FILE,">>filename") || die "Oops : $!";
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The double/single quote is all about interpolation. Special values (like variables, tabs & newlines) are parsed and then printed with double quotes. Single quotes force characters into lexicallity :) If you use a \n in single quotes, no newline is printed but the string \n. See perlop for more on interpolation.

Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.