SPUG: Some changes I'd like in Perl

Michael R. Wolf MichaelRunningWolf at att.net
Sat Nov 30 20:49:26 CST 2002

Tim Maher <tim at consultix-inc.com> writes:

> SPUGsters,
> On this Thanksgiving day, I'm giving thanks to The Larry and
> all his elves for the marvelous free invention that is Perl!

Here, here!

( or is it "Hear, hear!"?  I've only heard it, not seen it in print.)

> As an added bonus, some of you, especially those that don't
> use the AWK-ish -n/-p options much, might learn about some of

To crisp it up, I'd say
awk-ish -n (or sed-ish -p)

The -n is very awk-ish and the -n is very sed-ish.

And, I'll bet Aho, Kernighan, and Weinberger don't like AWK any more
than Larry likes PERL.  But I'll bet they don't have the distinction
that Perl is a language, and therefore a capitalized proper noun.  And
it's all run through perl, a command, that is Perl's

I could be mistaken.  Does the documentation refer to awk, Awk, or


> 1) There should be a way to tell the In-Place-Editing option
> (-i) to use a unique string in composing the file-extension on
> the backup filename.

My first thought was to create a module.  Before I could respond,
Yitzchak (A.K.A. Allen?) came up with a good start, then added the
sprintf(3)-like (or time(1)-like) percent arguments.  I like those

Let me add a few.

Definately have the module prevent overwrites of good data files.

Perhaps you could parameterize the module to do perform standard
backup file namings.

[I can't think of a 2-deep namespace without getting overwhelmed with
the GetOpt::* over-over-over-loaded namespace.  As an added benefit,
perhaps you cold ask Ingy to use Inline::Edit.  Naw, too confusing,
even if it is glamourous.  You'll have to get your 15 minutes

use InlineEdit;

use InlineEdit (:numeric_version:);  # use numeric increments in $^I
use InlineEdit (:PID_version:);      # use PID in $^I
use InlineEdit (:truncatable:);	     # allow empty output to truncate
use InlineEdit (:emacs_version:);    # use emacs bacup file names
use InlineEdit (:VMS_version:);      # use VMS version number syntax
use InlineEdit (:native_version);

The biggest unknown at this point in my knowledge would be how to
catch the @ARGV array shifting into $ARGV.  How does this happen with
respect to inline editing?  Is there a way to catch this shift as the
input file is being backed up and opened?  If so, these "well known"
renaming conventions, and over-write protections could be applied at
that point.

In addition, a stop_file_hook and start_file_hook function (ala emacs)
could be called to do whatever "interesting" checks or transformations
were necessary for the previous/next file.  For instance, a "chmod -w"
would be great to apply to the backup file.  At the very least, it
would allow the normal file system permissions to prevent the
double-shot foot shooting problem.  (And yes, I've done a similar
double-shot problem.  There *is* an _instinct_, in violation of my
_training_, that has me try it a second time to see if it works.
Perhaps I'm applying a hardware algorithm to software, but I grew up
in a hardware body in a hardware world gaining hardware experience.)


> Some time back, I asked Larry why there was no Awkish-FS
> variable, and he said "because my Mom says don't buy anything
> until you've felt the need for it on three separate occasions,
> and you're the first guy to ask for this!"  What a guy! 8-} 

Have you run a simple awk program through a2p(1) to see what Larry
would have given to his mother had she had grown up in awk-land?


> # Run following as "echo | ./scriptname"
> # To see that execution order matches statement numbers
> #! /usr/bin/perl -wln
> 	print 's2';	# I'm too lazy or deficient with VI 
> 			# to put this statement within the BEGIN,
> 			# so I'll place it here to get *even earlier
> 			# execution* (yea, right!)
> 	BEGIN	{ print 's1'; }
> 		  print 's3';
> 	END	{ print 's5'; }
> 	print 's4';	# ditto for locating this here
> Perl should say: "Warning: statement(s) placed before BEGIN block or 
> 	after END block will be run within implicit loop of -n/-p"

FYI -- My perl doesn't give me that warning:

This is perl, v5.6.1 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2001, Larry Wall

Binary build 633 provided by ActiveState Corp. http://www.ActiveState.com
Built 21:33:05 Jun 17 2002

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using `man perl' or `perldoc perl'.  If you have access to the
Internet, point your browser at http://www.perl.com/, the Perl Home Page.


Michael R. Wolf
    All mammals learn by playing!
        MichaelRunningWolf at att.net

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