Hi

I'm failing to use relative backreferences in \g-form in character classes.

Please note how [^\1] still works, but [^\g-1] fails.

Is there a better syntax within character classes?

I'm afraid I need to switch to negated look-aheads or hardcode different quotes.°

Debugger demo with perl-de0

The following regex tries to match quoted substrings in $1, the quote in $2

  DB<164> p $_
__'abc'__"def"__
  DB<165> x / ( (['"]) [^\2]*? \2 ) /gx     # OK
0  '\'abc\''
1  '\''
2  '"def"'
3  '"'
  DB<166> x / ( (['"]) [^\2]*? \g-1 ) /gx   # OK
0  '\'abc\''
1  '\''
2  '"def"'
3  '"'
  DB<167> x / ( (['"]) [^\g-1]*? \g-1 ) /gx # OOPS
Invalid [] range "\g-1" in regex; marked by <-- HERE in m/ ( (['"]) [^
+\g-1 <-- HERE ]*? \g-1 ) / at (eval 179)[c:/St\
rawberry/perl/lib/perl5db.pl:738] line 2.
 at (eval 179)[c:/Strawberry/perl/lib/perl5db.pl:738] line 2.
        eval 'no strict; ($@, $!, $^E, $,, $/, $\\, $^W) = @DB::saved;
+package main; $^D = $^D | $DB::db_stop;
  / ( ([\'"]) [^\\g-1]*? \\g-1 ) /gx;
' called at c:/Strawberry/perl/lib/perl5db.pl line 738
        DB::eval called at c:/Strawberry/perl/lib/perl5db.pl line 3138
        DB::DB called at -e line 1
  DB<168> p $]
5.032001
  DB<169>
[download]

FWIW: \g{-1} instead of \g-1 doesn't help either

This question is a follow-up to solution wanted for break-on-spaces (w/specifics)

update

°) or using (??{..})

SOLUTION

escaping the dash inside character classes helps, otherwise it's seen as a range

  DB<170> x / ( (['"]) [^\g\-1]*? \g-1 ) /gx
0  '\'abc\''
1  '\''
2  '"def"'
3  '"'
  DB<171> x / ( (['"]) [^\g{\-1}]*? \g-1 ) /gx
0  '\'abc\''
1  '\''
2  '"def"'
3  '"'
  DB<172> x / ( (['"]) [^\g2]*? \g-1 ) /gx
0  '\'abc\''
1  '\''
2  '"def"'
3  '"'
  DB<173>
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.