As long as you can mix numbers with letters the problem remains.
no, the signature does not allow to mix letters with numbers. if we allowed this, that means: 
++: /\A[a-z0-9]*\z/ -> /\A[a-z0-9]*\z/

[download]
, what is the difference between this addition and the addition in a 36-ary number system? (have fun with this link)
the only problem here is that the first character must not be a number, thus the awkward domains: 
kabel@linux:~> perl
my $num = "1hiho";
print ++ $num, $/;
2
kabel@linux:~>

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What about "-1"?
"-1" is an illegal input. harhar. ;-)

In reply to Re^4: $a++ allowed by $a-- is not ! why? by kabel
in thread $a++ allowed by $a-- is not ! why? by abhishes

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