# 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, $that='bar') { return scalar @_; } t_foo(0,undef,'Too few arguments'); t_foo(1,1,"One arg"); t_foo(2,2,"Two args"); t_foo(3,undef,"Too many arguments"); done_testing(); sub t_foo { my ($n_args, $exp, $desc ) = @_; my @args = ("","a".."z")[1..$n_args]; my $code = "foo(qw/@args/)"; my $got = eval $code; unless ($@) { is( $got, $exp, "<$code> \t $desc: \@_ == $got" ); } else { ok( $@ =~ $desc, "<$code> \t ERR: $desc: "); } } #diag "Show sig implementation:\n", B::Deparse->new()->coderef2text(\&foo);