use List::Permutor; 
 
my $string = 'ab12'; 
my $integer = 4; 
my $word = 'blue'; 
my @characters = split(//,$string); 
if(@characters > $integer) { 
    print "Error: too many characters is string\n"; 
    exit(0); 
} 
my $perm = new List::Permutor @characters; 
while (my @set = $perm->next) { 
   print join('',@set)."$word\n"; 
}

use Permutor; 
my $string = 'ab12'; 
my $integer = 4; my $word = 'blue'; 
my @characters = split(//,$string); 
if(@characters > $integer) {     print "Error: too many characters is string\n";     exit(0); } 
my $perm =new Permutor @characters; 
while (my @set = $perm->next) {    print join ('',@set)."$word\n"; } 

use Permutor;  
my $string = 'ab12';  
my $integer = 4; my $word = 'blue';  
my @characters = split(//,$string);  
if(@characters > $integer) {     print "Error: too many characters is string\n";     exit(0); }  
my $perm =new Permutor @characters;  
while (my @set = $perm->next) {    print join ('',@set)."$word\n"; }

package Permutor; 
 
use strict; 
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK); 
 
require Exporter; 
 
@ISA = qw(Exporter); 
@EXPORT = qw(); 
$VERSION = '0.022'; 
 
sub new { 
    my $class = shift; 
    my $items = [ @_ ]; 
    bless [ $items, [ 0..$#$items ] ], $class; 
} 
 
sub reset { 
    my $self = shift; 
    my $items = $self->[0]; 
    $self->[1] = [ 0..$#$items ]; 
    1;		# No useful return value 
} 
 
sub peek { 
    my $self = shift; 
    my $items = $self->[0]; 
    my $rv = $self->[1]; 
    @$items[ @$rv ]; 
} 
 
sub next { 
    my $self = shift; 
    my $items = $self->[0]; 
    my $rv = $self->[1];	# return value array 
    return unless @$rv; 
    my @next = @$rv; 
    # The last N items in @next (for 1 <= N <= @next) are each 
    # smaller than the one before. Move those into @tail. 
    my @tail = pop @next; 
    while (@next and $next[-1] > $tail[-1]) { 
        push @tail, pop @next; 
    } 
    # Then there's one more. Right? 
    if (defined(my $extra = pop @next)) { 
	# The extra one exchanges with the next larger one in @tail 
	my($place) = grep $extra < $tail[$_], 0..$#tail; 
	($extra, $tail[$place]) = ($tail[$place], $extra); 
	# And the next order is what you get by assembling the three 
	$self->[1] = [ @next, $extra, @tail ]; 
    } else { 
        # Guess that's all.... 
	$self->[1] = []; 
    } 
    return @$items[ @$rv ]; 
} 
 
1;

ab12blue 
ab21blue 
a1b2blue 
a12bblue 
a2b1blue 
a21bblue 
ba12blue 
ba21blue 
b1a2blue 
b12ablue 
b2a1blue 
b21ablue 
1ab2blue 
1a2bblue 
1ba2blue 
1b2ablue 
12abblue 
12bablue 
2ab1blue 
2a1bblue 
2ba1blue 
2b1ablue 
21abblue 
21bablue

 use List::Permutor; 
my $string = 'ab12'; 
my $integer = 4; 
my $word = 'blue'; 
my @characters = split(//,$string); 
if(@characters > $integer) { 
       print "Error: too many characters is string\n"; 
       exit(0); 
     } 
my $perm = new List::Permutor @characters; 
while (my @set = $perm->next) { 
open (output,"output.txt"); 
      print output join('',@set)."$word\n";   close (output);         }

use List::Permutor;  
my $string = 'ab12';  
my $integer = 4;  
my $word = 'blue';  
my @characters = split(//,$string);  
if(@characters > $integer) {  
       print "Error: too many characters is string\n";  
       exit(0);  
     }  
my $perm = new List::Permutor @characters; 
open (OUT, '>output.txt') or die "$!";  
while (my @set = $perm->next) {  
      print OUT join('',@set)."$word\n"; 
} 
close(OUT);