use strict;
my $str = 'A Nightmare On Elm Street 720p Bluray X264-Pahe In mkv mkv
Austin Powers International Man Of Mystery 480p Bluray 300mb-Pahe In mkv mkv
Death_warrant_1990_720p_bluray_x264_750mb-Pahe In mkv mkv
Die Frau Des Polizisten 720p Bluray X264-Pahe In mkv mkv';
my $regex = qr/ (\w\w\w) (\1)$/mp;
my $subst = '.\\1';
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