an example of using print as a debugging tool

fab4.pl

#!/usr/bin/perl
use strict;
use warnings;

my @Beatles = qw (John Paul George Ringo);
print "AT THE START Beatles are [@Beatles]\n";
my ($drummer, @vocals);
$drummer = pop @Beatles;
print "Drummer is $drummer and Beatles are [@Beatles] \n";
push @vocals, shift @Beatles;
print "Vocals are [@vocals] and Beatles are [@Beatles] \n";
push @vocals, shift @Beatles;
print "Vocals are [@vocals] and Beatles are [@Beatles] \n";
push @vocals, shift @Beatles;
print "Vocals are [@vocals] and Beatles are [@Beatles] \n";
unshift @Beatles, @vocals;
print "Vocals are [@vocals] and Beatles are [@Beatles] \n";
shift @Beatles;
print "Beatles are [@Beatles] \n";
push @Beatles, $drummer;
print "Beatles are [@Beatles] \n";
push @Beatles, 'Pete Best';
print "AT THE END Beatles are [@Beatles]\n";

The output I get is:

AT THE START Beatles are [John Paul George Ringo]
Drummer is Ringo and Beatles are [John Paul George]
Vocals are [John] and Beatles are [Paul George]
Vocals are [John Paul] and Beatles are [George]
Vocals are [John Paul George] and Beatles are []
Vocals are [John Paul George] and Beatles are [John Paul George]
Beatles are [Paul George]
Beatles are [Paul George Ringo]
AT THE END Beatles are [Paul George Ringo Pete Best]