#!/usr/bin/perl
# Fig. 4.10: fig04_10.pl
# Demonstrating the push, pop, shift and unshift functions.

# Use push to insert elements at the end of @array.
for ( $i = 1; $i <= 5; ++$i ) {
   push( @array, $i );            # add $i to end of @array
   print "@array\n";              # display current @array
}

# While there are more elements in @array, pop each element.
# Note the use of @array as a condition. When @array is empty, 
# the condition becomes false; otherwise, it is true.
while ( @array ) {
   $firstTotal += pop( @array );  # remove last element
   print "@array\n";              # display current @array
}

print "\$firstTotal = $firstTotal\n\n";

# Use unshift to insert elements at the front of @array.
for ( $i = 1; $i <= 5; ++$i ) {
   unshift( @array, $i );         # add $i to front of @array
   print "@array\n";              # display current @array
}

# While there are more elements in @array, remove each element
# with shift. 
while ( @array ) {
   $secondTotal += shift( @array );  # remove first element
   print "@array\n";                 # display current @array
}

print "\$secondTotal = $secondTotal\n";

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