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Re^4: No tools? Use Perl?!

by haukex (Archbishop)
on Jul 29, 2016 at 07:14 UTC ( [id://1168798]=note: print w/replies, xml ) Need Help??


in reply to Re^3: No tools? Use Perl?!
in thread No tools? Use Perl?!

Hi Boyd.Ako,

I don't know the specifics as to how /g works.

/g on an m// match is documented in perlop, in this case: "In scalar context, each execution of m//g finds the next match, returning true if it matches, and false if there is no further match." Since the regexp is being used in a while loop, without the /g modifier it would simply match the first occurrence every time and the loop would never end. With /g, the match advances through the string.

Alternatively: "The /g modifier specifies global pattern matching--that is, matching as many times as possible within the string. ... In list context, it returns a list of the substrings matched by any capturing parentheses in the regular expression." Without /g, it would only find the first match.

When you add the /g and the capturing group to codiac's code it works:

use warnings; use strict; my $text = <<'END'; <y><ReportHost>one</ReportHost> <x>test</x></y> <ReportHost> two </ReportHost> <ReportHost><z>thr</z>ee</ReportHost> END # m//g in scalar context while ($text=~ m{<ReportHost[^>]*>((?:(?!</ReportHost>).)*)</ReportHos +t>}sg) { print "a: \"$1\"\n"; } # m//g in list context my @m = $text=~ m{<ReportHost[^>]*>((?:(?!</ReportHost>).)*)</ReportHo +st>}sg; print "b: \"$_\"\n" for @m; __END__ a: "one" a: " two " a: "<z>thr</z>ee" b: "one" b: " two " b: "<z>thr</z>ee"

Hope this helps,
-- Hauke D

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