On 21/10/2011 19:16, Brandon McCaig wrote:
Thanks for the explanation, Rob. :)
use strict;
use warnings;
use v5.010;
my $data = 'aaa bbb ccc';
say $data;
for my $pattern (qw(bbb aaa ccc))
{
say join ' ', pos($data) // 'undef', $pattern,
scalar $data =~ /$pattern/g;
}
__END__
Would not have expected that. Neat. :)
It is perhaps counter-intuitive, but m//g in scalar context is a special
tool meant for simple parsing context-sensitive grammars. Take a look at
perldoc perlop
in the section titled "\G assertion".
Perhaps it seems more obvious that m//g would return a count of the
occurrences of the pattern in the target string, but
my $target = 'AAA BBB CCC DDD AAA XXX AAA QQQ BBB CCC BBB SSS';
my $result = $target =~ /AAA/g;
printf "result <%s>, pos %s\n", $result, pos($target) // 'undef';
yields
result <1>, pos 3
indicating that the string was found (a pattern match returns 1 for true
and '' for false) and the next m//g will start after three characters.
So no such luck. To find a pattern count you could either force list
context with the idiomatic
my $count = () = $target =~ /AAA/g;
which corresponds to the built in 'scalar' to force scalar context (but
sadly doesn't work in all situations).
Or write a simple loop
my $count;
$count++ foreach $target =~ /AAA/g;
But Perl 5 is a little broken in this respect, so it is probably best to
use m//g only in list context, if at all.
HTH,
Rob
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