nysus has asked for the wisdom of the Perl Monks concerning the following question:

I'm going through the perl regex tutorial meticulously to try to start filling in the gaps in my regex knowledge and I came across this little nugget: "don't" =~ / .+? \b{wb} /x;  # matches the whole string

I know what the "x" modifier does. But I have no earthly idea what \b{wb} character is or how it works. The tutorial provides no explanation except to say something vague about using it to match apostrophes. So I did a little searching and found this.

But this still sheds no light for me on why throwing this in after ".+?" should cause it to match the whole string "don't". Doesn't ".+?" just match "d"? Why should \b{wb} suck up the rest of the string?

$PM = "Perl Monk's";
$MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon Curate Priest Vicar";
$nysus = $PM . ' ' . $MCF;
Click here if you love Perl Monks

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Re: What does \b{wb} in a regex do?
by Fletch (Bishop) on Aug 24, 2020 at 14:13 UTC

    Regexp::Debugger can be elucidating. And remember ? making something non-greedy changes from "leftmost longest" to "leftmost shortest which still matches"; because the zero-space assertion follows it's got to backtrack and keep expanding until that's satisfied (by a transition from word-char to not-word-char).

    The cake is a lie.
    The cake is a lie.
    The cake is a lie.

[reply]
[d/l]
Re: What does \b{wb} in a regex do?
by nysus (Parson) on Aug 24, 2020 at 12:45 UTC

    OK, light bulb finally just went off after staring at this. The not greedy part sucks up the characters until it finds a unicode word boundary.

    $PM = "Perl Monk's";
    $MCF = "Most Clueless Friar Abbot Bishop Pontiff Deacon Curate Priest Vicar";
    $nysus = $PM . ' ' . $MCF;
    Click here if you love Perl Monks

[reply]
[reply]
[d/l]

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