Question: As part of a bigger program I've got a hash. I'm testing the program printing the keys but they are all duplicates, I don't know why

```
while ( my $line = <SEQ> ) {

  chomp $line;
  $line =~ s/>//;

  my ( @split1 ) = split( "\t", $line );

  foreach my $chr ( keys %position ) {

     #print Dumper \%position;
     print "$chr\n";

     foreach my $pos ( sort keys %{ $position{$chr} } ) {

        if ( $split1[0] =~ /$chr/ ) {
           #print "$chr\t$pos\n";
        }
     }
   }
}

```

`%position` is a nested hash, when I print the keys on `print "$chr\n";` they are all doubled and I don't understand why.

The file opened on handle `SEQ` looks like this:

```
>chr1\tACTGTAGTCTCATCCTAT...
>chr2\tACGTAGCTAGT....

```

and so on

Answer: 
It's not an ASCII character, it's likely an [emoji](https://en.wikipedia.org/wiki/Emoji). Emoji are part of Unicode and the actual glyph displayed to the user is open to interpretation by the platform displaying it. The spec suggests a name/description, but the implementation varies.

So while you may see a colored check mark, I see black & white. Other times, a single glyph will have multiple styles made available on a particular platform; for example, I can select multiple "skin" tones when I use a smiley face on my iPhone, but your Android device may only show a generic one.

Edit: The image edited into the original post is a perfect example. Using Chrome on Windows, I see a black check mark. The screenshot from Firefox shows green.
The symbols used here aren't ascii-encoded. They use the much more vast range of Unicode encoding. Ascii(extended) is restricted to a 256 symbol set.

The unicode interpretation for symbols/glyphs(small pictorial representation)(these ticks aren't characters), can vary for different platforms as some the range of unicode is open for usage and isn't set as global.

Which is why, while the unicode encryption remains the same for every device irrespective, the decryption is differently interpreted by different devices/online-platforms, allowing us to perceive either a coloured or a black symbol.