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What does it mean that regexps are greedy? How can I get around it?

by faq_monk (Initiate)
on Oct 08, 1999 at 00:25 UTC ( #667=perlfaq nodetype: print w/ replies, xml ) Need Help??

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

Most people mean that greedy regexps match as much as they can. Technically speaking, it's actually the quantifiers (?, *, +, {}) that are greedy rather than the whole pattern; Perl prefers local greed and immediate gratification to overall greed. To get non-greedy versions of the same quantifiers, use (??, *?, +?, {}?).

An example:

        $s1 = $s2 = "I am very very cold";
        $s1 =~ s/ve.*y //;      # I am cold
        $s2 =~ s/ve.*?y //;     # I am very cold

Notice how the second substitution stopped matching as soon as it encountered ``y ''. The *? quantifier effectively tells the regular expression engine to find a match as quickly as possible and pass control on to whatever is next in line, like you would if you were playing hot potato.

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