I think there are many arguments to be made in favor for using sub _ {} as syntactic sugar, but I forgot one of the most important:

Chaining sub {} requires commas as separators!

Please compare

use strict;
use warnings;

sub try (&;@) {};
sub catch (&;@){};
sub _ (&;@) {};


sub error_classes {
    return map { $_ => bless {}, $_ } @_;
}

use constant {
    error_classes qw(
        FileNotFoundError
        IsADirectoryError
    )
};



try {
    # your code here
} catch { FileNotFoundError } sub {
    # handle exception 
},                                      # extra comma needed
  catch { IsADirectoryError } sub {
      # handle exception
},
  catch {
      # all other types of exceptions
};

warn ('Should reach here');



try {
    # your code here
} catch { FileNotFoundError }_{
    # handle exception 
} catch { IsADirectoryError }_{
    # handle exception
} catch {
    # all other types of exceptions
};

warn('Should reach here')
[download]

Hence the OP was wrong and needs to be corrected.

If anyone sees a way to avoid the trailing commas (or fat commas), please feel free to show ...

Otherwise, this break in symmetry is just "meh" ...