The perltest program
--------------------

The perltest.pl script tests Perl's regular expressions; it has the same
specification as pcretest, and so can be given identical input, except that
input patterns can be followed only by Perl's lower case modifiers and certain
other pcretest modifiers that are either handled or ignored:

  /+   recognized and handled by perltest
  /++  the second + is ignored
  /8   recognized and handled by perltest
  /J   ignored
  /K   ignored
  /W   ignored
  /S   ignored
  /SS  ignored
  /Y   ignored

The pcretest \Y escape in data lines is removed before matching. The data lines
are processed as Perl double-quoted strings, so if they contain " $ or @
characters, these have to be escaped. For this reason, all such characters in
the Perl-compatible testinput1 file are escaped so that they can be used for
perltest as well as for pcretest. The special upper case pattern modifiers such
as /A that pcretest recognizes, and its special data line escapes, are not used
in the Perl-compatible test file. The output should be identical, apart from
the initial identifying banner.

The perltest.pl script can also test UTF-8 features. It recognizes the special
modifier /8 that pcretest uses to invoke UTF-8 functionality. The testinput4
and testinput6 files can be fed to perltest to run compatible UTF-8 tests.
However, it is necessary to add "use utf8; require Encode" to the script to
make this work correctly. I have not managed to find a way to handle this
automatically.

The other testinput files are not suitable for feeding to perltest.pl, since
they make use of the special upper case modifiers and escapes that pcretest
uses to test certain features of PCRE. Some of these files also contain
malformed regular expressions, in order to check that PCRE diagnoses them
correctly.

Philip Hazel
January 2012
