Dear Monks -

I have been looking into the world of code evaluation expressions of regular expressions recently. Still, I have not been able to come up with a single integrated regex that would match the following set of strings: "Any string of type /a+b+/ that contains exactly one more 'b' than 'a's". The regex I am looking for should therefore match abb, aabbb and aaabbbb but not ab, aab, aabb or abbb.

Clearly, the matching strings could be obtained from the following code: 
my @strings = qw( abb aabbb aaabbbb ab aab aabb abbb );

for ( @strings )
{
    our $a_counter = 0;
    our $b_counter = 0;

    if ( /(a(?{$a_counter ++;}))+(b(?{$b_counter ++;}))+/ && $b_counte
+r == $a_counter + 1 ) 
    {
        print "In '$_' there were $a_counter 'a's and $b_counter 'b's.
+\n";
    }
}

[download]
As mentioned above, however, I would like to consolidate the information contained in the regex and the if statement into a single regex. It really should match if and only if the number of 'b's exceeds the number of 'a's in the string by one. I don't want any over-generation that I need to filter in a subsequent if statement.

Could anyone please help me out here?

Thanks in advance for your help!

Pat

In reply to Integrating match counts into regex matching by pat_mc

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