use strict;
my $str = 'D:\\folder1\\folder2\\folder3\\Artifact\\Artifact-1.1\\
D:\\folder1\\folder2\\folder3\\Artifact\\Artifact-1.2\\
D:\\folder1\\folder2\\folder3\\Artifact\\Artifact-1.3\\
D:\\folder1\\folder2\\folder3\\Different_Artifact\\Different_Artifact-17.1\\
D:\\folder1\\folder2\\folder3\\Different_Artifact\\Different_Artifact-17.4\\
D:\\folder1\\folder2\\folder3\\Different_Content\\Different_Content-2.0\\
D:\\folder1\\folder2\\folder3\\folder4\\Different_Content\\Different_Content-2.0\\
D:\\folder1\\folder2\\folder3\\folder4\\Different_Content\\Different_Content-2.2\\';
my $regex = qr/^(.*\.)(\d+)\\(\n\1\d+\\)+$/mp;
my $subst = '$1$2\\\\';
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