Dear monks,
While I can loop through a string and solve this problem, I'm wondering if there is a regex that can do the same (I'm sure there is, likely using {}).

Given: 1) a string like $foo below; and 2) an arbitratry integer n which is < the count of some character $c (below $c = 'x') in $foo. Find, starting from the begining of $foo (^), the longest shortest string containing exactly n $c, (which will obviously be bound on both sides by $c). 
 
$foo = "xxx.x.....x......xxx...xx...x...xxx";

sub bar {
 my $n = shift;
 # do regex stuff on $foo ... 
 return $1 # or some such
}

# expected results for 
# n =
# 1 - x
# 2 - xx
# 3 - xxx
# 4 - xxx.x
# 5 - xxx.x.....x
# 6 - xxx.x.....x......x
# ... etc.

[download]

thanks, x

update I do mean shortest! and result for 4 fixed. My apologies.

In reply to regex finding shortest string containing n of $c by xipho

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