https://metacpan.org/release/LWALL/perl5.002b3/source/pod/perlre.pod does not contain the word POSIX, but the current perlre does. So as a first guess, Perl 5.002b3 did not support POSIX REs.

https://metacpan.org/release/GSAR/perl5.005-beta2/source/pod/perlre.pod also does not contain the word POSIX. https://metacpan.org/release/GSAR/perl-5.6.0/source/pod/perlre.pod does. So, my second guess is POSIX REs were introduced in 5.6.0. And indeed, https://metacpan.org/release/GSAR/perl-5.6.0/view/pod/perldelta.pod#POSIX-character-class-syntax-%5B:-:%5D-supported lists POSIX character class syntax as new feature for 5.6.0.

Alexander

There are various alternatives for YAPE::Regex::Explain

Could you give us a sample regex and tell us where and how it fails?

update

> It would be ideal if Perl 5.6 were a superset of Posix

not sure about that, but the supported character classes are listed in the head of the module's source.

does this help?

 
my $valid_POSIX = qr{
  alpha | alnum | ascii | cntrl | digit | graph |
  lower | print | punct | space | upper | word | xdigit
}x;
 
... 
 
my %macros = (
  # utf8/POSIX macros
  alpha => 'letters',
  alnum => 'letters and digits',
  ascii => 'all ASCII characters (\000 - \177)',
  cntrl => 'control characters (those with ASCII values less than 32)'
+,
  digit => 'digits (like \d)',
  graph => 'alphanumeric and punctuation characters',
  lower => 'lowercase letters',
  print => 'alphanumeric, punctuation, and whitespace characters',
  punct => 'punctuation characters',
  space => 'whitespace characters (like \s)',
  upper => 'uppercase letters',
  word => 'alphanumeric and underscore characters (like \w)',
  xdigit => 'hexadecimal digits (a-f, A-F, 0-9)',
);
[download]

I skimmed thru https://www.postgresql.org/docs/14/functions-matching.html and found some features which were new to me.

E.g. I've never heard of metacharacters \m or \M (?) I tested them and Perl will only see the escaped characters, i.e. literal m and M .

> It would be ideal if Perl 5.6 were a superset of Posix.

I'm afraid Postgres has another incompatible superset of Posix

Further searching revealed that PG is apparently using the TCL RE-engine and

> There are a number of important differences between Tcl Advanced Regular Expressions and Perl-style regular expressions. Tcl uses \m, \M, \y and \Y for word boundaries. Perl and most other modern regex flavors use \b and \B. In Tcl, these last two match a backspace and a backslash, respectively.

see here for more:

• https://www.regular-expressions.info/tcl.html
• https://www.regular-expressions.info/postgresql.html

I think you will be better off using something from the TCL toolchain.

"I think you will be better off using something from the TCL toolchain"

Patching YAPE::Regex::Explain could be easier, it's a rather compact module.

- Ron