What I dislike about Perl

PerlHate

My main problem with Perl is references and contexts. Most of the experienced programmers I've worked with find themselves unable to write or debug code that requires the use of these Perl concepts.

For example, my co-workers and I find it easy and intuitive to work with lists in Python:

    xs = [5, 6]
    xs.append(7)
    print xs[2]                      # prints 7
    xs.append([])                    # easy to append lists to other lists
    xs[3].append(6)                  # easy to append to the inner list
    some_func(12, "hello", xs, True) # easy to pass to a function

In Perl this would be way more complicated for reasons that are obvious to someone who knows Perl well, but a mystery to people who use Perl casually.

    $xs = [5, 6];                  # must be a reference
    push @$xs, 7                   # deference $xs as a list
    print "$xs->[2]"               # still not too bad
    push @$xs, []                  # add a nested list reference
    push @{$xs->[3]}, 6            # omgwtf?!
    some_func(12, "hello", $xs, 1) # not too bad

Understanding "push @{$xs->[3]}, 6" is asking a lot just to deal with a nested list that you need to pass to a function, especially compared to the easily understandable "xs[3].append(6)". For that matter, it's asking a lot to make you understand the difference between a list and a list reference. It's asking a lot to ask to understand the concept of "evaluating in a ___ context", especially when other languages manage to do the same things without these concepts.

Another thing about the above is how errors are handled.  Suppose that in the Python code we said

    xs[0].append(123)

We'd be trying to call the "append" method on an int, which would be a mistake and we'd get the exception

    AttributeError: 'int' object has no attribute 'append'

which is fairly helpful.  But suppose that we did the same thing in Perl:

    push @{$xs->[0]}, 123

Do you know what happens when we run that line?  Nothing.  There's no error, but everything is unchanged.  Here's what the Perl interpreter does:

First, it evaluates the scalar 5 in a list context.  Evaluating a scalar in a list context creates a new list with a single element, which is the value of the scalar.

Second, it appends the integer 123 to the new list, which now contains 5 as its first element and 123 as its second element.

Third, it immediately discards the list since we didn't store a reference to it anywhere, so Perl just garbage collects it and nothing is stored/saved anywhere.

I've seen people lose hours and hours to issues like this.  They have a line of code which is completely wrong, but the interpreter just silently does something nonsensical.