I can't replicate your failure or your success.

$ perl -e 'system("echo -e "\xFF\x08\x00" >> /dev/ttyACM0");'
Backslash found where operator expected at -e line 1, near ""echo -e "
+\"
    (Missing operator before \?)
Backslash found where operator expected at -e line 1, near "xFF\"
Backslash found where operator expected at -e line 1, near "x08\"
String found where operator expected at -e line 1, near "x00" >> /dev/
+ttyACM0""
syntax error at -e line 1, near ""echo -e "\"
Execution of -e aborted due to compilation errors.
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This fails for lack of permissions on my specific system (running as non-root):

$ perl -e 'system q{echo -e "\xFF\x08\x00" >> /dev/ttyACM0};'
sh: /dev/ttyACM0: Permission denied
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Writing to a regular file in my home directory works fine (except this echo does not support the same syntax as yours):

$ perl -e 'system q{echo -e "\xFF\x08\x00" >> ~/foo };'
$  cat ~/foo
-e �
$
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On Linux:

# perl -e 'system q{echo -e "\xFF\x08\x00" >> ~/foo };'
# cat ~/foo
�
#
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Multiple versions on differing platforms:

• This is perl 5, version 18, subversion 2 (v5.18.2) built for darwin-thread-multi-2level
• This is perl 5, version 14, subversion 4 (v5.14.4) built for x86_64-linux-64int
• This is perl, v5.10.1 (*) built for x86_64-linux-thread-multi

I have no idea how that would ever succeed with unescaped double quotes inside double quotes like that on any version. It just isn't valid Perl. How do I post a question effectively? is your friend (thanks jeffa and the SiteDocClan). Perhaps see also:

• http://stackoverflow.com/help/how-to-ask
• http://www.wikihow.com/Ask-a-Question-Intelligently
• http://www.inc.com/jeff-haden/5-ways-to-ask-the-perfect-question.html