It appears that there is an undocumented (as far as I can find) feature of the experimental (??{code}) regex feature. Namely that it makes the string that the regex is bound against available to the code block in a localised copy of $_. I think this is what the following shows: 

$test = 'the quick brown fox'; 
$_ = 8; 
if ( $test =~ m/^.*(??{print "$_\n"})/ ) { 
    print "**$_**\n"; 
}

[download]

Which produces 

the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox
the quick brown fox

[download]

To confirm the speculation I tried 

$test = 'the 1st quick brown fox'; 
$_ = 8; 
if ( $test =~ m/^.*(??{print "$_\n"})/ ) { 
    print "**$_**\n"; 
}

[download]

which gave 

the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
the 1st quick brown fox
**8**

[download]
Which I think demonstrates that because there is a '1' in the bound string which matches the '1' returned from the print in the code block, the match succeeds once the re_engine steps back far enough to find the match. Hence this time the if block is executed and the previous value of $_ is printed.

Could be a nice feature once you know its there.

Okay you lot, get your wings on the left, halos on the right. It's one size fits all, and "No!", you can't have a different color.
Pick up your cloud down the end and "Yes" if you get allocated a grey one they are a bit damp under foot, but someone has to get them.
Get used to the wings fast cos its an 8 hour day...unless the Govenor calls for a cyclone or hurricane, in which case 16 hour shifts are mandatory.
Just be grateful that you arrived just as the tornado season finished. Them buggers are real work.

In reply to Re: Re: Re: Re: Troubles with m!(??{substr(...)})! by BrowserUk
in thread Troubles with m!(??{substr(...)})! by jens

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