use strict;
my $str = '#1,0110,0010:~;0101_1000;0110_1001;0111_1010;1000_1011;1001_1100;1010_1101;1011_1110;1100_1111,~0000_00001_10010_20011_30100_40101_50110_60111_71000_81001_9';
my $regex = qr/(\d+)(?=(,|:).*?~.*?~.*?\1_(.))|#|,|:.*/p;
my $subst = '$3';
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