Hi.
I'm more of a newbie Perl programmer (1st post here also).
Today I (actually somebody else, but I'm posting this here now ;)) stumbled across some strange problem with regular expressions.

The code is simple: 
$_ = '511111';
print if /^(\d)\d{\1}$/;

[download]
The first digit of the string in $_ indicates the number of digits following.
(For example, 233 should match, 42143 also, but 324 should not.)
However, the code above does not work.
We know how to work around this problem, the problem is NOT to find a solution for this. We simply want to know WHY this does not work.
It seems that this is not something trivial.


Furthermore, we were wondering:
If the regexp above would work, what if the first TWO or more digits would indicate how many digits follow? (meaning that >= 10 digits follow)
How could you stuff that into one regexp? (it's also just a theoretical question, but an interesting one IMHO).

Thanks in advance.

In reply to RegExp madness by palandir

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