...
package main;

use Interpolation;
my $foo = new Foo;

my $CALL = {};
tie %$CALL, 'Interpolation::general', sub {
	my $obj = shift();
	my $cmd = shift();
	no strict 'refs';
	$obj->$cmd(@_);
}, '$$@->$';

print "x $CALL->{$foo}->{bar}\n";
print "x $CALL->{$foo}->{bar}{1}\n";
print "x $CALL->{$foo}->{bar}{1,2}\n";