regcomp.c	AOK

  Strange *+?{} on zero-length expression	[S_study_chunk]
	/(?=a)?/

  %.*s matches null string many times   	[S_regpiece]
	$a = "ABC123" ; $a =~ /(?=a)*/'

  /%.127s/: Unrecognized escape \\%c passed through"	[S_regatom] 
  	/\m/

  Character class syntax [. .] is reserved for future extensions [S_regpposixcc]

  Character class syntax [= =] is reserved for future extensions [S_checkposixcc]

  Character class syntax [%c %c] belongs inside character classes [S_checkposixcc] 
  

  

__END__
# regcomp.c [S_regpiece]
use warnings 'unsafe' ;
my $a = "ABC123" ; 
$a =~ /(?=a)*/ ;
no warnings 'unsafe' ;
$a =~ /(?=a)*/ ;
EXPECT
(?=a)* matches null string many times at - line 4.
########
# regcomp.c [S_study_chunk]
use warnings 'unsafe' ;
$_ = "" ;
/(?=a)?/;
no warnings 'unsafe' ;
/(?=a)?/;
EXPECT
Strange *+?{} on zero-length expression at - line 4.
########
# regcomp.c [S_regatom]
use warnings 'unsafe' ;
$a =~ /\m/ ;
no warnings 'unsafe' ;
EXPECT
Unrecognized escape \m passed through at - line 3.
########
# regcomp.c [S_regpposixcc S_checkposixcc]
use warnings 'unsafe' ;
$_ = "" ;
/[:alpha:]/;
/[.bar.]/;
/[=zog=]/;
/[[:alpha:]]/;
/[[.foo.]]/;
/[[=bar=]]/;
/[:zog:]/;
no warnings 'unsafe' ;
/[:alpha:]/;
/[.foo.]/;
/[=bar=]/;
/[[:alpha:]]/;
/[[.foo.]]/;
/[[=bar=]]/;
/[:zog:]/;
/[[:zog:]]/;
EXPECT
Character class syntax [: :] belongs inside character classes at - line 4.
Character class syntax [. .] belongs inside character classes at - line 5.
Character class syntax [. .] is reserved for future extensions at - line 5.
Character class syntax [= =] belongs inside character classes at - line 6.
Character class syntax [= =] is reserved for future extensions at - line 6.
Character class syntax [. .] is reserved for future extensions at - line 8.
Character class syntax [= =] is reserved for future extensions at - line 9.
Character class syntax [: :] belongs inside character classes at - line 10.
Character class [:zog:] unknown at - line 19.