Re^4: Parsing Problems

in reply to Re^3: Parsing Problems
in thread Parsing Problems

Thank you for your reply. This is helpful as I've traced the error to how Perl is handling the modules, @INC, and referencing subroutines.

What my code is supposed to do is apply different sets of transformations to a text file based on options specified from the command-line:

modes.pl [rawtext] [style] [mode](one, two, etc.) [1st variation](a, a_prime, b, etc.) [2nd variation]

"style" is one of several directories containing nine .pm files. Each .pm file has at least the subroutines "first" and "flex." The other subroutines are variations.

Here is the code that I'm using to load the modules:

package modes;
my $lP;
my $modCount = 0;
BEGIN{
 $lP = "$ARGV[1]";
}
use lib $lP;
if(opendir(LIB, $lP)){
 foreach my $l (readdir(LIB)){
  unless ($l !~ /^(.*)\.pm$/){
   eval qq~require ~ . $ARGV[1] . qq~::~ . $1 . qq~;~;
   print $@;
  }
 }
}
[download]

The error that code produces (given: ./modes.pl "filename" english three a b) in Perl 5.26.1 (error does not occur in 5.18.2) is the following:

Can't locate english/eight.pm in @INC (you may need to install the eng
+lish::eight module) (@INC contains: english /home/******/perl5/lib/pe
+rl5/5.26.1/x86_64-linux-gnu-thread-multi /home/*********/perl5/lib/pe
+rl5/5.26.1 /home/***/perl5/lib/perl5/x86_64-linux-gnu-thread-multi /h
+ome/******/perl5/lib/perl5 /etc/perl /usr/local/lib/x86_64-linux-gnu/
+perl/5.26.1 /usr/local/share/perl/5.26.1 /usr/lib/x86_64-linux-gnu/pe
+rl5/5.26 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.26 /usr/sh
+are/perl/5.26 /home/****/perl5/lib/perl5/5.26.0 /home/*****/perl5/lib
+/perl5/5.26.0/x86_64-linux-gnu-thread-multi /usr/local/lib/site_perl 
+/usr/lib/x86_64-linux-gnu/perl-base) at (eval 5) line 1.
[download]

Setting $lP to the fully qualified PWD (or simply "." since the "english" directory is located here) fixes that error, but the subroutines are still undefined:

Undefined subroutine &modes::three::flex

I'm not sure why this is. I will change my code based on your recommendations, but I don't understand it well enough myself to do so yet. I borrowed the module loading code from another programmer years ago simply because it did what I needed - I never fully understood it.

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Re^5: Parsing Problems (updated) by haukex (Archbishop) on May 15, 2019 at 22:01 UTC
Based on what you've posed here, you definitely don't need to use the `eval` with `require BAREWORD;`, `require "/path/to/filename.pm";` would be much easier in your case. Also, note that despite its several caveats, a glob might be easier than opendir in this case. Here's an example, where `$stylespath` is an absolute pathname (see do for the rules on when `@INC` will be searched and when it won't): `use File::Glob 'bsd_glob'; my $style = $ARGV[1]; die "bad style" unless $style=~/\A\w+\z/; require $_ for bsd_glob("$stylespath/$style/.pm");` [download] the subroutines are still undefined: `Undefined subroutine &modes::three::flex` I'm not sure why this is.* What `package` statement (if any) does `english/eight.pm` start with? If it's e.g. `package eight;`, then a `sub flex` in that file declares a subroutine whose full name is `&eight::flex`. Note that the AM post does not name one caveat of UNIVERSAL's `can` method, which is that it also searches the package's ancestry via @ISA for that method - if you don't set `@ISA` in your packages, it's fine, but if you do, then you need to be aware of this. If you want to avoid that, then this is IMO one of those rare cases where symbolic refs can help: `my $package = 'eight'; my $subref = do { no strict 'refs'; \&{$package.'::flex'} };`. Update: That you've traced it down to this issue also helps explain what you described in your root node, that you see a difference between 5.18 and 5.26: Removal of the current directory (".") from @INC may explain your issue. But my suggestions above still stand!	[reply] [d/l] [select]

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Re^5: Parsing Problems (updated)
by haukex (Archbishop) on May 15, 2019 at 22:01 UTC

Based on what you've posed here, you definitely don't need to use the eval with require BAREWORD;, require "/path/to/filename.pm"; would be much easier in your case. Also, note that despite its several caveats, a glob might be easier than opendir in this case. Here's an example, where $stylespath is an absolute pathname (see do for the rules on when @INC will be searched and when it won't):

use File::Glob 'bsd_glob';

my $style = $ARGV[1];
die "bad style" unless $style=~/\A\w+\z/;
require $_ for bsd_glob("$stylespath/$style/*.pm");
[download]

the subroutines are still undefined: Undefined subroutine &modes::three::flex I'm not sure why this is.

What package statement (if any) does english/eight.pm start with? If it's e.g. package eight;, then a sub flex in that file declares a subroutine whose full name is &eight::flex.

Note that the AM post does not name one caveat of UNIVERSAL's can method, which is that it also searches the package's ancestry via @ISA for that method - if you don't set @ISA in your packages, it's fine, but if you do, then you need to be aware of this. If you want to avoid that, then this is IMO one of those rare cases where symbolic refs can help: my $package = 'eight'; my $subref = do { no strict 'refs'; \&{$package.'::flex'} };.

Update: That you've traced it down to this issue also helps explain what you described in your root node, that you see a difference between 5.18 and 5.26: Removal of the current directory (".") from @INC may explain your issue. But my suggestions above still stand!

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