You might not be able to inject anything using it, but a NUL can confuse things: 
$ perl -e '$qs=chr(0); system( qq{echo "$qs"} );'
Syntax error: Unterminated quoted string

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I wonder if there's a UNICODE character other than " and \ whose UTF-8 encoding contains the byte 34 (") or 92 (\)... ( No, doesn't appear to be. I bet that if I looked into how UNICODE points are transformed into UTF-8, I'd find the presence of those bytes impossible. The 8th bit seems to always be set. )

In reply to Re^2: quoting for system() and friends by ikegami
in thread quoting for system() and friends by pileofrogs

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