Raku: Using topic variable (from a 'for') inside a regex

Question

I have this code that works as expected:

my @words = 'foo', 'bar';
my $text = 'barfoo';

for @words -> $to-regex {
    $text ~~ m/ ($to-regex) {say "matched $0"}/;
}

It prints:

matched foo
matched bar

However, if I try to use topic variable on the for loop, as in:

for @words { # implicit "-> $_", AFAIK
    $text ~~ m/ ($_) {say "matched $0"}/;
}

I get this:

matched barfoo
matched barfoo

Same results using postfix for:

$text ~~ m/ ($_) {say "matched $0"}/ for @words; # implicit "-> $_", AFAIK

Is this a special case of the topic variable inside a regex?

Is it supposed to hold the whole string it is matching against?

Note that regexes in raku are dreadfully slow and if you can avoid them you should. Here for instance, if one is just looking for presence of a substr in a str, using the index method is worth considering. — Holli, Oct 17 '20 at 12:11

score 8 · Accepted Answer · answered Oct 17 '20 at 03:55

The smart-match operator has 3 stages

So it isn't a special case for a regex, it is how ~~ always works.

for 1,2,3 {
    $_.print;
    'abc' ~~ $_.say
}
# 1abc
# 2abc
# 3abc

1 Answers1