use strict;
my $str = '6876786786 GFS8978976 I
6786786767 DDF78676 I
4343245443 SBSSK67676 I
8393372263 SBSSK56565 I
6545434347 DDF7878333 I
6757650000 SBSSK453 I';
my $regex = qr/(\d+)\s+([A-Z]+)(\d+)\s+(\w+)/p;
my $subst = '$1+$2+$3+$4';
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