Hi David,

I'm not sure if I understand your problem ...

... the call foo("a") is exactly doing what I expect, i.e. @_ == 1

Anything else - like pushing an optional $that into @_ - wouldn't really be backwards compatible.

And the number you seem to want is static, it's the sum of obligatory arguments + defaulted ones.

(maybe you want to make a feature request to be able to introspect the signature)

FWIW, when interested you can look into the implementation with B::Deparse ...

# https://perlmonks.org/?node_id=11119273
use strict;
use warnings;
use feature qw(signatures);
no warnings qw(experimental::signatures);

use B::Deparse;
use Test::More;


sub foo ($this, $that='bar') {
    return scalar @_;
}


is(
   foo(1),
   1,
   "one arg"
  );

is(
   foo(1,2),
   2,
   "two args"
  );


done_testing();


warn "Show implementation:\n", B::Deparse->new()->coderef2text(\&foo);

[download]

C:/Perl_524/bin\perl.exe -w d:/exp/pm_signatures.pl 
ok 1 - one arg
ok 2 - two args
1..2
Show implementation:
{
    BEGIN {${^WARNING_BITS} = "\x54\x55\x55\x55\x55\x55\x55\x55\x55\x5
+5\x55\x55\x55\x55\x54\x55\x05"}
    use strict;
    use feature 'signatures';
    die sprintf("Too many arguments for subroutine at %s line %d.\n", 
+(caller)[1, 2]) unless @_ <= 2;
    die sprintf("Too few arguments for subroutine at %s line %d.\n", (
+caller)[1, 2]) unless @_ >= 1;
    my $this = $_[0];
    my $that = @_ >= 2 ? $_[1] : 'bar';
    ();
    return scalar @_;
} at d:/exp/pm_signatures.pl line 32.

Compilation finished at Tue Jul 14 14:25:41

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

UPDATE

expanded code with tests

In reply to Re: Contents of @_ using subroutine signatures with default values (not a bug) by LanX
in thread Contents of @_ using subroutine signatures with default values by davido

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.