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Re: Can't match negated words.

by perlgags78 (Acolyte)
on Jun 24, 2004 at 17:17 UTC ( #369421=note: print w/replies, xml ) Need Help??

in reply to Can't match negated words.

Can anyone explain what is mean by clustering and capturing?
Or even the difference between them?
I'm reading the docs and came across this.
This is for clustering, not capturing; it groups
subexpressions like "()", but doesn't make backreferences
as "()" does. So
@fields = split(/\b(?:a|b|c)\b/)

is like

@fields = split(/\b(a|b|c)\b/)


Replies are listed 'Best First'.
Re^2: Can't match negated words.
by Roy Johnson (Monsignor) on Jun 24, 2004 at 17:38 UTC
    Clustering is grouping, like in an algebraic expression. Parentheses limit how far back and forward an alternator (vertical bar) applies:
    /foo|bar/; # Matches "foo" or "bar" /fo(o|b)ar/;# Matches "fooar" or "fobar"
    Grouping also allows quantifiers to apply to more than one atom:
    /foo{3}/ # Matches "foooo" /(foo){3}/ # Matches "foofoofoo"
    Capturing is storing the parenthesized portion of the match somewhere that you can refer back to it (as $1, or as an element of the list returned by a match, for example). Ordinary parentheses are capturing parentheses. Special parentheses (any that have a ? after the opening paren) are non-capturing. All parentheses group their contents.

    We're not really tightening our belts, it just feels that way because we're getting fatter.

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