The best thing to do, as CERT recommends, is to "sanitize" and only allow what you need: 
$_ = "the\\/bad\$dataStuff"; # your data of course :)
$OK_CHARS='-a-zA-Z0-9_.@'; # allowed characters
s/[^$OK_CHARS]/_/go; # replace invalid chars with _
$user_data = $_; # sanitized version
print $user_data;
# output: the__bad_dataStuff

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Excellent article from CERT.

In reply to Re: validation of posted data. by amir
in thread validation of posted data. by hostux

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