#!/usr/bin/perl

use strict;
use warnings;

my @A = (234, 405, 55, 1900);

print "\n", shift(@A);           # Prints 234
#print "\n", shift(234, 4, 55, 1900);        # Error: Can't overwrite the array, because it's fixed.
#print "\n", shift( split(/\+/, '12+34+56+78') );  # Error: Can't overwrite the array, because it's fixed.

my $X = 3;

print "\n", INCREMENT($X);   # Prints 4.
#print "\n", INCREMENT(3);    # Error: Can't overwrite 3, because it's fixed.

print "\nNOW: $X";                 # Prints 4. No error.
print "\n", INCREMENT( $X + 3 );   # Prints 8. No error.
print "\nTHEN: $X";                # Prints 4. No error.
#print "\n", shift( @A, split(/\+/, '12+34+56+78') );  # Error. Can't do this.

# Kind of weird. That's not what I expected. :P

exit;

sub INCREMENT { ++$_[0]; }