Re^3: Using a capture in /(?{...})/

The warning comes from the fact that Perl can't tell if (?{ ... }) matches any characters or not, so it's possible you're putting a quantifier on a zero-width assertion.

Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

Comment on Re^3: Using a capture in /(?{...})/ Download Code

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Re^4: Using a capture in /(?{...})/ by ikegami (Patriarch) on Jul 26, 2005 at 00:07 UTC
You mean `(??{ ... })`. (`(?{ ... })` is always zero-width.) Ok, the warning makes sense. There are (at least) two ways of hidding it: 1) Use `no warnings 'regexp'`, or 2) refactor the regexp to hide that particular instance of the warning while leaving others on. For example, `$re0 = qr/ (??{ $re1 })* /x;` [download] can be written as: `$re0 = qr/ (??{ $re1 }) (??{ $re0 }) \| # Nothing /x;` [download] and `$re0 = qr/ (??{ $re1 })+ /x;` [download] can be written as: `$re0 = qr/ (??{ $re1 }) (??{ $re0_ }) /x; $re0_ = qr/ (??{ $re1 }) (??{ $re0_ }) \| # Nothing /x;` [download] and `$re0 = qr/ (??{ $re1 })? /x;` [download] can be written as: `$re0 = qr/ (??{ $re1 }) \| # Nothing /x;` [download]	[reply] [d/l] [select]

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Re^4: Using a capture in /(?{...})/
by ikegami (Patriarch) on Jul 26, 2005 at 00:07 UTC

You mean (??{ ... }). ((?{ ... }) is always zero-width.) Ok, the warning makes sense. There are (at least) two ways of hidding it:

1) Use no warnings 'regexp', or

2) refactor the regexp to hide that particular instance of the warning while leaving others on. For example,

$re0 = qr/
          (??{ $re1 })*
       /x;
[download]

can be written as:

$re0 = qr/
          (??{ $re1 }) (??{ $re0 })
          |
          # Nothing
       /x;
[download]

and

$re0 = qr/
          (??{ $re1 })+
       /x;
[download]

can be written as:

$re0  = qr/
           (??{ $re1 }) (??{ $re0_ })
        /x;

$re0_ = qr/
           (??{ $re1 }) (??{ $re0_ })
           |
           # Nothing
        /x;
[download]

and

$re0  = qr/
           (??{ $re1 })?
        /x;
[download]

can be written as:

$re0  = qr/
           (??{ $re1 })
           |
           # Nothing
        /x;
[download]

[reply]
[d/l]
[select]