use strict;

my @a = ( 0,1,2,3 ) ; my @b = ( 1,2,3,4 );
my @x = ( 0,1,2,3 ) ; my @y = ( 1,2,3,4 );
my @r = reverse @a;

my $next = 0 ; my $first = 0;

my $first = shift @a ;
print "a $#a shift ",$first,"->";
while ( $next = shift @a )
                    { print ",",$next }
print "\n";

$first = shift @b ;
print "b $#b shift ",$first,"->";
while ( $next = shift @b )
                    { print ",",$next }
print "\n";

$first = pop @x ;
print "x $#x pop ",$first,"->";
while ( $next = pop @x )
                    { print ",",$next }
print "\n";

$first = pop @y ;
print "y $#y pop ",$first,"->";
while ( $next = pop @y )
                    { print ",",$next }
print "\n";

$first = pop @r ;
print "r $#r pop ",$first,"->";
while ( $next = pop @r )
                    { print ",",$next }
print "\n";

Gives --- >>>>> See line starting x
$ perl test.pl 
a 2 shift 0->,1,2,3
b 2 shift 1->,2,3,4
x 2 pop 3->,2,1
y 2 pop 4->,3,2,1
r 2 pop 0->,1,2,3