From type/IO/Path

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multi sub dir(*%_)
multi sub dir(IO::Path:D $path, |c)
multi sub dir(IO()       $path, |c)
method dir(IO::Path:D: Mu :$test = $*SPEC.curupdir)

Returns the contents of a directory as a lazy list of IO::Path objects representing relative paths, filtered by smartmatching their names (as strings) against the :test parameter. The path of returned files will be absolute or relative depending on what $path is.

Since the tests are performed against Str arguments, not IO, the tests are executed in the $*CWD, instead of the target directory. When testing against file test operators, this won't work:

dir('mydir', test => { .IO.d })

while this will:

dir('mydir', test => { "mydir/$_".IO.d })

NOTE: a dir call opens a directory for reading, which counts towards maximum per-process open files for your program. Be sure to exhaust returned Seq before doing something like recursively performing more dir calls. You can exhaust it by assigning to a @-sigiled variable or simply looping over it. Note how examples below push further dirs to look through into an Array, rather than immediately calling dir on them. See also IO::Dir module that gives you finer control over closing dir handles.

Examples:

# To iterate over the contents of the current directory: 
for dir() -> $file {
    say $file;
}
 
# As before, but include even '.' and '..' which are filtered out by 
# the default :test matcher: 
for dir(test => *) -> $file {
    say $file;
}
 
# To get the names of all .jpg and .jpeg files in the home directory of the current user: 
my @jpegs = $*HOME.dir: test => /:i '.' jpe?g $/;

An example program that lists all files and directories recursively:

sub MAIN($dir = '.') {
    my @todo = $dir.IO;
    while @todo {
        for @todo.pop.dir -> $path {
            say $path.Str;
            @todo.push: $path if $path.d;
        }
    }
}

A lazy way to find the first three files ending in ".p6" recursively starting from the current directory:

my @stack = '.'.IO;
my $raku-files = gather while @stack {
    with @stack.pop {
        when :d { @stack.append: .dir }
        .take when .extension.lc eq 'p6'
    }
}
.put for $raku-files[^3];