use Data::Dumper;
$filename = "codes.txt";
open $fh1, $filename or die "can't open $filename :  $!\n";
$filename2= "./context.txt";
open $fh2, $filename2 or die "can't open $filename2 :  $!\n";

chomp(@Ids=<$fh1>);
LABEL: while(chomp(my $line = <$fh2>)){
    foreach my $codeid (@Ids){
        if($line =~ /-$codeid-/){
            s/Event id -(\d+)-/$data{$codeid}=$1/e && next LABEL while(<$fh2>);
        }
    }
}
print Dumper \%data;