The  (*F) operator was introduced with 5.10. Prior to that,  (?!) can be used. 

>perl -wMstrict -le
"for my $n (4 .. 9) {
   my $str = qq{I have 5 apples, $n oranges, and 8 limes.};
   print qq{'$str'};
   next unless $str =~ m{
     (\d+) \s+ apples  \D+
     (\d+) \s+ oranges \D+
     (\d+) \s+ limes
     (?(?{ $1 < $2 && $2 < $3 }) | (*F) )
     }xms;
   print qq{'$2'};
   }
"
'I have 5 apples, 4 oranges, and 8 limes.'
'I have 5 apples, 5 oranges, and 8 limes.'
'I have 5 apples, 6 oranges, and 8 limes.'
'6'
'I have 5 apples, 7 oranges, and 8 limes.'
'7'
'I have 5 apples, 8 oranges, and 8 limes.'
'I have 5 apples, 9 oranges, and 8 limes.'

[download]

In reply to Re^3: How to use "less than" and "greater than" inside a regex for a $variable number by AnomalousMonk
in thread How to use "less than" and "greater than" inside a regex for a $variable number by Polyglot

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