It’s always baffled me that Perl subroutines behave differently when called from inside the Package vs. outside.
The use case may be obvious but I’ll say it: you write a small utility routine that you want to call as $pack->func(1); and from within the Package as func(1);;
The problem of course is that when called as $pack->func(1); the first arg will the object itself and when called as func(1); from within the package the first arg will be “1.”
There’s a very simple solution:
shift if ((ref $_[0]) eq __PACKAGE__);
Here’s a simple example:
#!/usr/bin/perl -w
#
package Pack;
sub new {
my $c = shift;
my $self = {};
bless $self, $c;
return $self;
}
sub func {
shift if ((ref $_[0]) eq __PACKAGE__);
my $a = shift;
print "passed in: $a\n";
}
sub call_func {
print "calling func from inside ", __PACKAGE__, ":\n";
func(2);
}
1;
my $p = new Pack;
print "calling func from main:\n";
$p->func(1);
$p->call_func();
Try commenting the “shift” line in sub func() and see how it behaves differently.