use strict;
my $str = 'Should work for:
(1,2,3)
(1,2,3,4)
((1,2),3,4)
(((1,2,3),4),5)
({x},{y},{z})
(1,(2,3),4)
((1,2),(3,4),5)
((1,2),3,(4,5))
(1,(2,(3,4),5))
(1,(2,({3},4),5))
(1,{{1},{1,2}},3)
Should not work for:
(1,2)
(10,10)
(1,10)
((1,2),3)
(((1,1),1),1)
({0},1)
({{x},{x,y}},z)';
my $regex = qr/(\((({(?:[^{}]+|(?-1))+})|\((?:[^(),]+,[^(),]+)\)|[^(){},]+)(?:,(?2))+),/mp;
my $subst = '($1),';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html