Thus the following command is evaluated regardless of filename:

$error ||= "Unexpected signer 'GOODSIG 86125876138571635 ClientKey' is
+ not ''."
        unless ('GOODSIG 86125876138571635 ClientKey' =~ m/\Q\E/);
[download]

yet sometimes an error is created, sometimes not.

If the error is created, that's because it is set elsewhere. The code you gave will not change $error when $expected_signer is an empty string. That's because m/\Q$foo\E/ will match anything when $foo is empty. (Every string contains an empty string.) In this snippet, $error is only set unless the match is true. Since it is true, $error isn't set.

Update: Changed "Every string matches an empty string" to "Every string contains an emptry string." The latter is what I really meant (as the context implies.) My thanks go to Enlil for spotting it.

-sauoq
"My two cents aren't worth a dime.";

Please run the code below and see if you get the same output as I do (also below). If so, I would like to know why it is behaving as it is.

#!/usr/local/perl -w

use strict;

my $filename1 = 'FILE.pgp';
my $filename2 = 'FILE.gpg';

my $signer    = 'Some person <someone@this.com>';
my $exp_sender= '';

my $new_filename1 = $filename1;
   $new_filename1 =~ s/(\.gpg)|(\.encrypted)/\.decrypted/;

print ".PGP FILE ERROR:'$signer' is not '$exp_sender'.\n"
        unless ($signer =~ m/\Q$exp_sender\E/);

my $new_filename2 = $filename2;
   $new_filename2 =~ s/(\.gpg)|(\.encrypted)/\.decrypted/;

print ".GPG FILE ERROR:'$signer' is not '$exp_sender'.\n"
        unless ($signer =~ m/\Q$exp_sender\E/);

my $new_filename3 = $filename1;
   $new_filename3 =~ s/(\.gpg)|(\.encrypted)/\.decrypted/;

print ".PGP ERROR, why the second time but not the first?:'$signer' is
+ not '$exp_sender'.\n"
        unless ($signer =~ m/\Q$exp_sender\E/);

1;
[download]

And below is the out put I get from the above script

$ perl match_test.pl
.GPG FILE ERROR:'Some person <someone@this.com>' is not ''.
.PGP ERROR, why the second time but not the first?:'Some person <someo
+ne@this.com>' is not ''.
[download]

the_Don
...making offers others can't rufuse.

Strangely enough, you've hit a regular expression gotcha.

The empty regular expression has a special meaning: try again the last regular expression that successfully matched. What is perhaps less obvious is that perl checks for an empty expression after interpolating variables, such as the \Q$exp_sender\E in your example.

Here's a snippet to illustrate:

  "test" =~ /t/;  # successful match
  my $var = "";
  print "matched 't'\n" if "t" =~ /\Q$var\E/;
  print "matched 'u'\n" if "u" =~ /\Q$var\E/;
[download]

A couple of alternative approaches, depending on what you're trying to achieve:

  print "'$signer' is not '$exp_sender'\n"
      unless $signer eq $exp_sender;
  print "'$signer' is not '$exp_sender'\n"
      unless index($signer, $exp_sender) >= 0;
  print "'$signer' is not '$exp_sender'\n"
      unless $exp_sender eq '' || $signer eq $exp_sender;
[download]

Hugo

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.

I think that I have a pretty good understanding of basic perl and programming theories. What I don't understand is why what appears to be identical calls with identical data is resulting in two different outcomes.

• True, I should add .pgp as a file that will result in a .decrypt extension... or just add .decrypt on the end regardless of what the original extension is.
• The program dies at the end with one call to an email routine and messages if there was an error. Basically the same thing, and yes a little bit more processing, nothing too bad.
• The program is checking with a regex against a list of signed keys that we have. The validity here lies in the PGP encryption system, not the power of Perl regex.
• My possible intent was to have the null character imply that as long as a trusted, signed key was recognized as the signature then not to worry, but specifiying a particular sender in the perl would add some error checking in the system.

What more do you want of the code? It will be hard for me to post the entire code since it is company material, but if you have a thought process about something going onn, I will surely put up pertinent pieces. In all there is at most 100 lines that are executed.

the_Don
...making offers others can't rufuse.

I think that I have a pretty good understanding of basic perl and programming theories.

If you think 'FILE.gpg' and 'FILE.pgp' are "identical data", then I would have to dispute your claim.
Furthermore, do you realize that m/\Q\E/ matches everything, and thus that

  $expected_sender = '';
  if ( $signer =~ /\Q$expected_sender\E/ )
[download]

will always be true?
It is entirely unclear why/how your section 1 and section 2 could be related. Since you "know" that they are, you have useful information which you're not sharing. Do you want us to help, or not?

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.