Perl 6 has a new .wrap method just for this sort of thing.

In Perl 5, this technique comes to my (sleepy) mind:

use strict;
use warnings;

sub greet {
    my ($name) = @_;

    print "Hi, $name!\n"
      or return 'Shame :(';

    return 'Glory !';
}

sub wrap_the_sub {
    my ($sub_name) = @_;
    my $sub_ref = \&{$sub_name};
    my $wrapping_sub = sub {
        my @args = @_;
        print "Entering '$sub_name'\n";
        my $rc = $sub_ref->(@args);
        print "Exiting '$sub_name'\n";
        # Really need some wantarray() trick there...
        return $rc;
    };
    no strict 'refs';
    no warnings 'redefine';
    *{$sub_name} = $wrapping_sub;
}

wrap_the_sub('greet');

my $result = greet('Util');
print "Result was: '$result'\n";
[download]

Output:

Entering 'greet'
Hi, Util!
Exiting 'greet'
Result was: 'Glory !'
[download]