#!/usr/bin/perl
use strict;
use warnings;

my %hash=();

# input
my $inputfile = 'nv.txt';
open IN, '<',$inputfile 
     or die "Could not open $inputfile : $!"; 
while (<IN>) {
  my ($key, $val) = split (/:/,$_,2);
  $hash{$key} .= $val;
}

# output
for my $key (keys %hash){
  my $outputfile = "output_$key";
  $outputfile =~ s{/}{-}g;
  print "Writing to $outputfile\n";
  open OUT,'>',$outputfile 
       or die "Could not open $outputfile : $!";
  print OUT $hash{$key};
  close OUT;
}
__DATA__
test/right/case1:12: //comment
test/right/case1:344: //comment
test/wrong/case3:123:  //comment