# used by munge function to safely interpolate
# $1, $2 etc into the replacement string
sub _safeswitch {
    my @P = (undef,$1,$2,$3,$4,$5,$6,$7,$8,$9);
    $_[0] =~ s/\$(\d)/$P[$1]/g;
    $_[0];
}

##</code><code>##

# used by munge function to safely interpolate
# $1, $2, etc. into the replacement string
sub _safeswitch {
  my %seen;
  @seen{@+} = (undef) x @+;
  my @P;
  {
    no strict 'refs'; # allow $$_ to be $1, $2, etc.
    no warnings 'unitialized'; # allow undef as $$_
    @P = map { $$_ } undef, 1 .. scalar keys %seen;
  }
  $_[0] =~ s/\$(\d+)/$P[$1]/g;
  $_[0];
}

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;

my $str = 'abcdefghijklmnopqrstuvwxyz';
my $pat = '(.).(.).(.)..(.).(.)(.)(.).(.)(.)(.).(.)(.)(.)(.).+';
my $repl = '$5$14$12$13 $1$8$9$13$4$3$11 $10$3$11$7 $4$1$2$6$3$11';

print munge( $str, $pat, $repl ), "\n";

sub munge {
  my($str, $pat, $repl) = @_;
  $str =~ s/$pat/_safeswitch($repl)/eg;
  return $str;
}

# used by munge function to safely interpolate
# $1, $2, etc. into the replacement string
sub _safeswitch {
  my %seen;
  @seen{@+} = (undef) x @+;
  my @P;
  {
    no strict 'refs'; # allow $$_ to be $1, $2, etc.
    no warnings 'uninitialized'; # allow undef as $$_
    @P = map { $$_ } undef, 1 .. scalar keys %seen;
  }
  $_[0] =~ s/\$(\d+)/$P[$1]/g;
  $_[0];
}

exit;