tom@wintermute tom $ perl -c t
syntax error at t line 17, near "else"
t had compilation errors.
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if ( exists $list{$location} ) {
    my $value = $list{$location};
    $value++;

    $list{$location} = $value;
}
elsif ( $list{$location} eq "" ) {
    if ( exists $list{Unknown} ) {
        my $value = $list{Unknown};
        $value++;
        $list{Unknown} = $value;
    }
}
else {
    $list{Unknown} = "1";
}
else {
    $list{$location} = "1";
}
[download]

You can't have two else blocks, so you probably meant to have an else block in the second if statement, like so:

if ( exists $list{$location} ) {
    my $value = $list{$location};
    $value++;

    $list{$location} = $value;
}
elsif ( $list{$location} eq "" ) {
    if ( exists $list{Unknown} ) {
        my $value = $list{Unknown};
        $value++;
        $list{Unknown} = $value;
    }
    else {
        $list{Unknown} = "1";
    }
}
else {
    $list{$location} = "1";
}
[download]

And just in case the difference isn't clear (kinda hard to see), here's a diff:

*** 10,18 ****
          $value++;
          $list{Unknown} = $value;
      }
! }
! else {
!     $list{Unknown} = "1";
  }
  else {
      $list{$location} = "1";
--- 10,18 ----
          $value++;
          $list{Unknown} = $value;
      }
!     else {
!         $list{Unknown} = "1";
!     }
  }
  else {
      $list{$location} = "1";
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Update Reworded diff sentence to make it sound less harsh and more like original meaning.