use strict;
my $str = '/text1/text2/text3/wanted_text/text5/text6';
my $regex = qr%(/[^/]+){3}/([^/]+).*%mp;
my $subst = '\\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