#! perl -slw
use strict;
use Time::HiRes qw[ time ];

sub nar_substitute {
    my @numeric_chars = ( 0 .. 9 );
    my $message = shift;
    my @numeric_matches = ($message =~ m/\{\\d\d+\}/g);
    foreach (@numeric_matches) {
        my $substitution = $_;
        my ($substitution_count) = ($substitution =~ m/(\d+)/);
        my $number = '';
        for (1..$substitution_count) {
            $number .= $numeric_chars[int rand @numeric_chars];;
        }
        $message =~ s[\Q$substitution][$number]e;
    }
    return $message;
}

sub buk_substitute{
    my $s = shift;
    $s =~ s[\{\\d(\d+)\}][ substr int( 1e10 + rand 1e10 ), 1, $1 ]ge;
    return $s
}

our $O //= 0;
$|++;

my $start = time;

for my $fname ( glob 'templ*.txt' ) {
    printf "\rProcessing $fname";
    my $file = do{ local( @ARGV, $/ ) = $fname; <> };
    $file = $O ? buk_substitute( $file ) : nar_substitute( $file );
    open O, '>', "modified/$fname" or die $!;
    print O $file;
    close O;
}

printf "\n\nTook %.6f secs\n", time() - $start;