#!/usr/bin/perl -w
use strict;                            # be good!

sub hello;
sub goodbye;
sub imlate;

my $LOG;                               # dummy log this example...
$::DBUG = shift;                       # take from command-line this example

sub ::f {                              # pretty-print sub entry/exit
    my $n = "\n";                      # shortcut for newline
    my $enter = shift;                 # entering -> 1, exiting -> 0
    $enter && $::FUNC_LEVEL++;         # increment global var if entering
    # print > times global function level var plus name of calling function
    $::DBUG && print(                  # print to screen
        ( ($enter) ? ">" : "<" ) x $::FUNC_LEVEL . 
        ( " " ) . 
        ( caller(1) )[3] . $n          # calling function name
    );
    $::DBUG && $LOG && LOG->print(     # print to log
        ( ($enter) ? ">" : "<" ) x $::FUNC_LEVEL . 
        ( " " ) . 
        ( caller(1) )[3] . $n
    );
    $enter || $::FUNC_LEVEL--;         # decrement global var if exiting
};

sub hello {                            # standard usage
    ::f(1);                            # function entry
    for(1..2) {
        print "hello!\n" . goodbye();  # call some sub...
    }
    ::f(0);                            # function exit
};

sub goodbye {                          # a tricky bit...
    ::f(1);                            # regular entrance
    ::f(0);                            # must execute BEFORE return
    return "goodbye!\n";
};

sub imlate {                           # just for giggles...
    ::f(1);
    print "i'm late!\n" x 3;
    ::f(0);
};

hello();
imlate();

##</code><code>##

> main::hello
>> main::goodbye
<< main::goodbye
hello!
goodbye!
>> main::goodbye
<< main::goodbye
hello!
goodbye!
< main::hello
> main::imlate
i'm late!
i'm late!
i'm late!
< main::imlate