Here is a simple way to do it by keeping track of how deep you are into parenthesis' and what depth your match occured at:
use strict;
my $str = "((A,B),C,(D,E))";
foreach my $m (qw(A B C D E)) {
print $m." => ".FindMinParens($m,$str)."\n";
}
sub FindMinParens{
my $match = shift;
my $string = shift;
my @start_pos;
my $depth = -1;
# keep matching parens or $match
while ($string=~/([()]|$match)/g) {
if ($1 eq "(") {
# record opening paren positions
push @start_pos,pos($string);
}
elsif ($1 eq ")") {
# if we reached the closing parens for the minimum pair
# get the sub string and exit
if ($#start_pos == $depth) {
my $start = $start_pos[-1];
my $len = pos($string) - $start -1;
return substr($string,$start,$len);
}else{
pop @start_pos;
}
}
else {
# store depth of $match
$depth = $#start_pos;
}
}
return "";
}
__OUTPUT__
A => A,B
B => A,B
C => (A,B),C,(D,E)
D => D,E
E => D,E
