It's not apparent what you are trying to do. Here's your code cleaned up with the syntax errors removed:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my %hash=();
%hash=(
##keys between "" because of dots
"M01.001" =>["M01.001"],
"M01.001.111" =>["M01.001.111"],
"M01.001.111.111" =>["M01.001.111.111"],
"M01.002" =>["M01.002"],
"M01.002.003" =>["M01.002.003"],
);
print Dumper(%hash), "\n";
for my $k(sort keys %hash){
my $temp = reverse($k);
$temp =~ s/^\d{3}\.?//;
my $t= reverse ($temp);
if (exists $hash{$t}){
$hash{$k}[1] += 1;
}
}
print Dumper(%hash);
__END__
As for the $hash{$k}[1] += 1; "not working", it is working. It might not be doing what you wanted, but it's doing what somebody would expect, which is to create a second element in the array $hash{$k}, and then add 1 to it, to produce the result 1. If you meant to add 1 to the string "M01.001", what exactly do you think that means? You can't add the integer 1 to a string. It doesn't make sense.
