# 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];
}
[download]

If I read the above correctly, it'll only handle 9 sets of capturing parens, and it's possible that we may have matched more than 9 sets.

My fix is to dynamically build @P to size.

# 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];
}
[download]

And a test:

#!/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;
[download]

• my %seen
  
• no warnings 'unitialized';
  
• allow multiple digits in s/// in _safeswitch
  
• add test case
  

Incidentally, the line @seen{@+} = (undef) x @+; is a faster way to build
such a hash than the various equivalents ( %seen = map { $_ => undef } @+;
most notable among them for being popular and 4x slower).

I discovered this just today ;)

blyman
setenv EXINIT 'set noai ts=2'