And I thought the \d{11,}? was the invented bit. I'll have to play with that sometime.

You should, the future of all new perl regex features rests upon that syntax

I don't see the relation between your link and that bit of the regex. However, that said, your skepticism of its utility seems justified. I tried to find a use for it, but I haven't been able to make \d{4,}? act any differently than \d{4}. It's either a useless construct, or a failure of my imagination in coming up with an appropriate test case.

Putting aside what YAPE::Regex::Explain says about it, when I looked at it originally, I thought "Yack! Perl is gonna bitch about that weird '?' character". I could think of a couple other interpretations, so I put together a bit of code to check 'em out:

my @tests = (               
    'First case',           
    '123456789second & third case',
);                          
                            
for my $t (@tests) {        
    print "\nchecking '$t'\n";                                        
+          
    if ($t=~/(\d{4,}?)(.*)/)   { print "A: $1, $2\n"; }
    if ($t=~/(\d{4,}?)(.*?)$/) { print "B: $1, $2\n"; }
}
[download]

The other interpretations I could think of were:

• An optional set of 4 or more digits, kind of like (?:\d{4,})?. If true, the first case would give us:

  A: , First case'
  [download]

• Exactly 4 digits, like \d{4}, giving us:

  checking '123456789second & third case'
  A: 1234, 56789second & third case
  B: 1234, 56789second & third case
  [download]

• 4 or more digits, with as few as possible, yielding:

  checking '123456789second & third case'
  A: 1234, 56789second & third case
  B: 123456789, second & third case
  [download]

On reading the ...explain() output, I thought that I could perhaps make the third case come about. But what I actually got was:

$ perl xxxyyyzzz.pl

checking 'First case'

checking '123456789second & third case'
A: 1234, 56789second & third case
B: 1234, 56789second & third case
[download]

So I'm thinking that my initial surprise was justified, even though it's syntactically correct.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

It's different if there is some following match condition:

use strict;
use warnings;

for my $reg ('(x\d{3,}?)', '(x\d{3,}?x)', '(x\d{3,})', '(x\d{3})') {
    for my $str ('xx', 'x12x', 'x123456x', 'x12x x123x') {
        print "Matched using $reg: $1\n" if $str =~ $reg;
    }
}
[download]

Prints:

Matched using (x\d{3,}?): x123
Matched using (x\d{3,}?): x123
Matched using (x\d{3,}?x): x123456x
Matched using (x\d{3,}?x): x123x
Matched using (x\d{3,}): x123456
Matched using (x\d{3,}): x123
Matched using (x\d{3}): x123
Matched using (x\d{3}): x123
[download]

True laziness is hard work