package Foo;
use strict;

sub new { return bless {f => 'foo'}, $_[0]; }
sub foo { shift; print "@_\n"; }
1;

package main;
use strict;

my $a = new Foo();

my $f = $a->{f};
no strict qw(subs);
$a->$f('foobar');

1;
__END__