this gives me an error David like it does not understand what is trying to be opened? Below is the error:

./23file.pm: open: not found
./23file.pm: open: not found
./23file.pm: open: not found
./23file.pm: syntax error at line 4: `)' unexpected
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any clues? Thanks.

Here is the code I am using

open MASTER, "file3" or die "cant't open master file: $!\n";
open SUBSET, "file2" or die "can't open subset file: $!\n";
open OUT, ">outfile" or die "can't open output file: $!\n";
while ( my $sline = <SUBSET> ) {
    chomp $sline;
    my ( $subkey, $subvals ) = split /:/, $sline, 2;
    my ( $mkey, $mvals );
    while ( my $mline = <MASTER> ) {
        chomp $mline;
        ( $mkey, $mvals ) = split /:/, $mline, 2;
        last if $mkey eq $subkey;
    }
    print OUT join ":", $subkey, $subvals, $mvals;
}
close SUBSET;
close MASTER;
close OUT or die "couldn't close outfile: $!\n";
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