#!/usr/bin/env perl

# @(#) p1	Demonstrate list entry identification, movement.

use warnings;
use strict;
use List::MoreUtils qw( first_index );

my ( $debug, @a, @original, $t1, $t2 );
$debug = 1;
$debug = 0;

my ($want) = "cat";
@original = qw/ pig goat catastrophe cat dog turkey deer /;

@a = @original;

print "\n";
print " For simple string equality, \"cat\", constant, then variable:\n";
print "\n";
print " Constant, just to see a simple example:\n";
print "a (original   ) is :@a:\n";

$t1 = first_index { $_ eq "cat" } @a;
print $t1, "\n" if $debug;

$t2 = splice( @a, $t1, 1 );
print $t2, "\n" if $debug;

unshift @a, $t2;
print "a (for unshift) is :@a:\n";

print "\n";
print " Now with variables, a more likely situation:\n";
@a = @original;
print "a (original   ) is :@a:\n";

$t1 = first_index { $_ eq $want } @a;
print $t1, "\n" if $debug;

$t2 = splice( @a, $t1, 1 );
print $t2, "\n" if $debug;

unshift @a, $t2;
print "a (for unshift) is :@a:\n";

print "\n";
@a = @original;
print "a (original   ) is :@a:\n";

$t1 = first_index { $_ eq $want } @a;
print $t1, "\n" if $debug;

$t2 = splice( @a, $t1, 1 );
print $t2, "\n" if $debug;

push @a, $t2;
print "a (for push   ) is :@a:\n";

print "\n";
@a = @original;
print "a (original   ) is :@a:\n";
unshift @a, splice( @a, ( first_index { $_ eq $want } @a ), 1 );

print "a (single line) is :@a:\n";

@a = @original;

print "\n";
print " For string match regular expression, /$want/:\n";
print "\n";
print "a (original   ) is :@a:\n";

$t1 = first_index { $_ =~ m/$want/ } @a;
print $t1, "\n" if $debug;

$t2 = splice( @a, $t1, 1 );
print $t2, "\n" if $debug;

unshift @a, $t2;
print "a (for unshift) is :@a:\n";

exit(0);

% ./p1

 For simple string equality, "cat", constant, then variable:

 Constant, just to see a simple example:
a (original   ) is :pig goat catastrophe cat dog turkey deer:
a (for unshift) is :cat pig goat catastrophe dog turkey deer:

 Now with variables, a more likely situation:
a (original   ) is :pig goat catastrophe cat dog turkey deer:
a (for unshift) is :cat pig goat catastrophe dog turkey deer:

a (original   ) is :pig goat catastrophe cat dog turkey deer:
a (for push   ) is :pig goat catastrophe dog turkey deer cat:

a (original   ) is :pig goat catastrophe cat dog turkey deer:
a (single line) is :cat pig goat catastrophe dog turkey deer:

 For string match regular expression, /cat/:

a (original   ) is :pig goat catastrophe cat dog turkey deer:
a (for unshift) is :catastrophe pig goat cat dog turkey deer: