use strict;
my $str = 'Xbo
Play
Sep2018
/////////////////////////
reregg
95959
1151
Zbo
Tlay
Jul2018';
my $regex = qr/(?:^[A-Za-z].*\R\K|(?!^)\G)(?=(?:[A-Za-z].*\R)*(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\d{4}\b)/mp;
my $subst = '0\\n';
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