Even though I am pretty good at Perl regex, I am learning Perl regex so I can understand the Perl Monks threads on the subject.

I found https://perldoc.perl.org/perlretut entitled perlretut - Perl regular expressions tutorial.

Everything was fine until I came upon this passage in https://perldoc.perl.org/perlretut#Using-character-classes.

(This is a tutorial. It probably belongs in a footnote.)

For natural language processing (so that, for example, apostrophes are
+ included in words), use instead \b{wb}</p>

"don't" =~ / .+? \b{wb} /x;  # matches the whole string

[download]

What is going on here?

Regex101 is no help.

I wrote a test to try to understand it. It only caused me more confusion.

use warnings;
use strict;
use feature qw{ say };

if ("don't" =~ / (.+?) (\b{wb}) /x) {  # matches the whole string
    print "It matches\n";
    say $1;
    say $2;
}
else {
    print "It doesn't match\n";
}

if ("don't" =~ / (.+?) /x) {  # It no longer matches the whole string
    print "It matches\n";
    say $1;
}
else {
    print "It doesn't match\n";
}

Output:
It matches
don't

It matches
d

[download]

Who is going to attempt natural language processing with a couple of lines of Perl regex in 2025?

In reply to perlretut - Perl regular expressions tutorial curveball by Cow1337killr

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