use strict;
my $str = 'c.2 Employed population below international poverty line, by sex and age (%) Age: 15+
b.1 Employed population below international poverty line, by sex and age (%) Age: 15+
a.1 Employed population below international poverty line, by sex and age (%) Age: 15+
1. Employed population below international poverty line, by sex and age (%) Age: 15+
1.2 Employed population below international poverty line, by sex and age (%) Age: 15+
1.1.1 Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.1.C.1) Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.3) Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.4.C.13) Employed population below international poverty line, by sex and age (%) Age: 15+';
my $regex = qr/^(?:[a-z]|\d+)(?:\.\d+)*\.?\s*(?:\([A-Z]\.\d+(?:\.[A-Z]\.\d+)*\)\s*)?/mp;
my $subst = '';
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