Monkey patching can be quite useful in another way, too. It allows to generate lots of functions in a loop instead of writing them one-by-one. I sometimes use this in some wrapper modules, so i can for example log all database calls for debugging.

BEGIN {
    # Auto-magically generate a number of similar functions without ac
+tually
    # writing them down one-by-one. This makes changes much easier, bu
+t
    # you need perl wizardry level +10 to understand how it works...
    my @simpleFuncs = qw(commit rollback errstr);
    my @stdFuncs = qw(do quote pg_savepoint pg_rollback_to pg_release)
+;

    for my $a (@simpleFuncs){
        no strict 'refs'; ## no critic (TestingAndDebugging::ProhibitN
+oStrict)
        *{__PACKAGE__ . "::$a"} = sub { $_[0]->checkDBH(); return $_[0
+]->{mdbh}->$a(); };
    }

    for my $a (@stdFuncs){
        no strict 'refs'; ## no critic (TestingAndDebugging::ProhibitN
+oStrict)
        *{__PACKAGE__ . "::$a"} = sub { $_[0]->checkDBH(); if($_[0]->{
+isDebugging}) {print STDERR $_[0]->{modname}, " ", $_[1], "\n";}; ret
+urn $_[0]->{mdbh}->$a($_[1]); };
    }
};
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