Re: Negating Regexes: Tips, Tools, And Tricks Of The Trade

[imp]

I was experimenting with this and came up with the following .

use strict;
use warnings;

my $pattern = qr/abc/;

my $negative = qr<
  (??{ 
    /$pattern/ ? qr/\A$/ : qr//;
  })
>x;


my $text = 'abcdef';
if ($text =~ /$negative/) {
  print "matched $text\n";
}

This strategy uses (??{ code }) to evaluate the current string against the regex you wish to negate.
If the pattern matches it returns a regex that matches an empty string.
Otherwise it returns a regex that matching anything.

I'm not sure how safe this strategy is though. Can someone who knows more about perl's regex engine comment on whether the above is appropriate?