inst_trace();
foo();
bar('test');

sub foo { print "Hello "; }
sub bar { print "world @_\n"; }

sub inst_trace {
    for(keys %{*::}) {
        if(*{$_}{CODE}) {
            my $sub = $_;
            my $ref = \&{$sub};
            *{$sub} = sub { print STDERR "$sub called\n"; &$ref; };
        }
    }
}