use strict;
my $str = '//source/project/file.cs#232
path "//source/project/file.initial.config.cs#232"';
my $regex = qr/(\/(\w+)(?:\..*)(\w{2,3})\#)/p;
my $subst = '$2.$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