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 Need Help??
Well, I can make a ruleset that seems to fit:
1. Always keep the first two numbers intact
2. If any zeros start at position 3, remove them all.
3. If you didn't do that, then if two or more zeros start after position 3, truncate them to a single 0
4. If you didn't do either of the first two techniques, then remove a single 0 starting at position 3 or later entirely.

What happens if a single 0 starts at position 3? What does '35010333356' turn into?

Here's my code:
```#!/usr/bin/perl

use strict;
use warnings;
use Test::More;

my %output_for
= ( '215000007801' => '21507801',
'300000324002' => '30324002',
'890000457651' => '89457651',
'210004563401' => '214563401',
'201045139158' => '20145139158', );

plan tests => scalar keys %output_for;

while ( my (\$input, \$correct_output) = each %output_for ) {
my \$orig_input = \$input;
\$input = &compress_numstring( \$input );
is( \$input, \$correct_output, "Solved '\$orig_input'" );
}

sub compress_numstring {
my \$starting_num = shift;
return \$starting_num
unless(defined \$starting_num && \$starting_num =~ /^(\d{2})(\d+)/);
my( \$keep, \$modify ) = (\$1,\$2);
( \$modify =~ s/^0+// ) ||
( \$modify =~ s/0{2,}/0/ ) ||
( \$modify =~ s/(?<!0)0([1-9]|\$)/\$1/ );
return \$keep . \$modify;
}
It passes the validation test, but it may fail further tests since the rules aren't clearly spelled out.
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Chatterbox?
 [1nickt]: kgb not quite as simple as ... and ...; are interchangeable. There are edge cases, shown in perlsyn. [1nickt]: Hm well actually I guess it's not the trailing semi-colon that's at issue there, it's disambiguation between the ellipsis and the binary flip-flop [1nickt]: Although the example given does not produce an error as stated, on my perl. [1nickt]: perl -wE 'say for map { ... } 1..3;' # "Unimplemented at -e line 1" ... perlsyn says that should throw a syntax error...

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