I’ve been enjoying Perl lately, but I’ve never looked at the implementation before. It was a pleasant surprise to see that the github repo has a pretty complete history, all the way to Perl 1. In no time, I found myself wondering:

Can I build Perl 1 today?

I checked out a worktree of Perl 1, patch 14. This was the last revision in the Perl 1 series available, and it is dated Feb 1, 1988. Let’s see if I can build it with gcc 10 on Fedora 32.

git worktree add ../perl1 a4de7c03d0bdc29d9d3a18abad4ac2628182ed7b

Configure

Ok, the README file says to run Configure. I don’t expect it to work unmodified, plus I’m scared it will throw files around, so I read through it first. Some observations:

  • It says to trim the comments manually if your shell doesn’t do that. Apparently in 1988 not all bourne shells understood comments.
  • On line 30 it’s still just trying to double-check it is running in a bourne shell. Stuff we take for granted today!
  • It’s very conversational. It will echo things like “I found it here, of all places.” This would happen more often in the 80’s, I think, than it does today. There must have been a theory that conversational programs were a good idea–maybe with an eye toward the eventual HAL9000. TeX, for example, also sometimes speaks to you as if it’s an entity.
  • It warns you that make depend will take awhile, when of course I know it’s going to run instantaneously. Modern computing has benefits!

Running Configure, the only time it really got stumped was when it tried to find libc. Rather than giving up, it just asked me for the path. I knew from skimming the script that it wanted an libc.a static archive, but I tried giving it “/lib64/libc-2.31.so” anyway. It actually seemed to be happy.

I ran “make depend” and it put some garbage lines in the makefile (where files depend on nonsense like “<built-in>” and “<command-line>”. I just deleted these lines manually.

Make

The make went very smoothly, all things considered. Almost all the issues I needed to correct were due to incomplete function prototypes and a few overlaps between provided functions and standard functions. I also needed to adjust the LDFLAGS to link to libcrypt. Soon enough, I had a working Perl.

I’ll include the patch between my version and the git source at the bottom of this post. The entire unified diff is only about 200 lines long.

The distribution has a set of tests in a “t” directory, and nearly all of them pass. One bug this binary has, in particular, is that you can’t run a one liner… using the “-e” argument leads to a segmentation fault. Since it runs scripts ok, I did not try to track that issue down. It’s not going to be the Perl I use day-to-day, after all!

The Perl 1 Language

This is what I was most interested to understand: is Perl version 1 anything like the Perl I know? Looking at the test scripts, the distinctive flavor of Perl is decidedly there.

  • Sigils? check.
  • Lists and hashes? check.
  • Double-quote interpolation? check.
  • Diamond operator? check.
  • if/unless/while/until as statment modifiers? check.
  • list arguments flatten? partially.
  • ‘last’ instead of ‘break’? check.
  • formats? check.
  • Regex? check.
    • choose-your-own-delimiters? yep
  • Topic variables $_ and @_? absolutely.
  • Subs without signatures, shifting arguments from @_? yes.

Let me cut to the chase: the test suite looks so much like Perl that most of the tests pass when I run Perl 5.30 on them! Here are the main differences I noticed:

  • You seem to need more parens to make the parser happy than you need in a current Perl. Example: $j = join ':', (1,2,3,4); does not work in Perl 1; you need to put parens around the arguments to “join.”
  • There don’t seem to be any auto-quoting barewords. So use $h{'name'}, not $h{name}.
  • I expected to need to call subs with &mysub();, but in Perl 1 the incantation is actually do mysub();. That’s the main thing that causes Perl 5 to fail when running the test suite.

… and obviously no lexical variables or modules, etc. There are things missing, clearly, but nearly everything in Perl 1 made it to Perl 5 unchanged.

No Need to Continue

I had initially planned to get Perl 2 and 3 to compile as well, and chart the progression toward familiar Perl. I don’t need to: the first Perl is so Perl that it would be a waste of time. I really didn’t expect that.

The Patch

If you’d like to build it yourself, maybe this patch will help you: perl1-modern.patch. It should apply against a checkout of commit a4de7c03d0bdc29d9d3a18abad4ac2628182ed7b in the perl5 github repository (Perl 1, patch 14).