use strict;
use warnings;

for my $package (qw(testpackage)) {
    my $st_name = "main::" . $package . "::";
    my $symbol_table = do {
        no strict 'refs';
        *{$st_name}{HASH};
    };

    while( my ($k, $v) = each %$symbol_table ) {
        if( $package->can($k) ) {
            my $st_fname = $st_name . $k;
            my $fref = do {
                no strict 'refs';
                *{$st_fname}{CODE}; # from Memoize.pm :: _make_cref()
            };

            next unless $fref and ref $fref eq "CODE";
            next if defined prototype $fref; # I'm ignoring prototypes

            my $newf = sub {
                my ($r, @r);

                warn "<beginfunc name=\"$k\">\n";

                if( wantarray ) {
                    @r = $fref->(@_);

                } else {
                    $r = $fref->(@_);
                }

                warn "</endfunc>\n";

                return $r unless wantarray;
                @r;
            };

            do {
                no strict 'refs';
                local($^W) = 0;       # ``Subroutine $install_name redefined at ...''
                *{$st_fname} = $newf; # also from Memoize.pm :: memoize()
            }
        }
    }
}

testpackage->f1();
testpackage->f2();

package testpackage;

use strict;

sub f1 {
    print "f1!\n";
}

sub f2 {
    print "f2!\n";
}