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"

[download]

Hope this helps,
-- Hauke D

In reply to Re^4: No tools? Use Perl?! by haukex
in thread No tools? Use Perl?! by Boyd.Ako

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