my $file_name = ...;
my $kwd       = ...;

open my $fh, '<', $file_name
   or die("Unable to open file \"$file_name\": $!\n");

local $/ = "";
while (<$fh>) {
   chomp;
   my @fields = split /:/, $_;
   if ($fields[1] eq $kwd) {
      print "$_\n\n";
   }
}

##</code><code>##

my $fn_in  = ...;
my $fn_out = ...;
my $kwd    = ...;

open my $fh_in, '<', $fn_in
   or die("Unable to open file \"$fn_in\": $!\n");

open my $fh_out, '>', $fn_out
   or die("Unable to create file \"$fn_out\": $!\n");

local $/ = "";
while (<$fh_in>) {
   chomp;
   my @fields = split /:/, $_;
   if ($fields[1] eq $kwd) {
      print $fh_out "$_\n\n";
   }
}