Accessing C's printf is also possible with the latest FFI::Platypus without calling an external binary:
use warnings;
use strict;
use POSIX qw/LC_NUMERIC/;
use FFI::Platypus 1.07;
my $ffi = FFI::Platypus->new( api => 1 );
$ffi->lib(undef); # search current process for symbols (libc etc.)
my $loc = $ffi->function( setlocale => ['int','string'] => 'string' )
->call(LC_NUMERIC, ""); # set according to environment vars
print "Locale: $loc\n";
$ffi->attach( [ printf => 'cprintf_i' ] => ['string']
=> ['int'] => 'int' ); # variadic function
cprintf_i("%'d\n", 42e6);
# ##### UPDATE - Wrapped in a sub #####
$ffi->attach( [ snprintf => 'c_snprintf_i' ]
=> ['opaque','size_t','string'] => ['int'] => 'int' );
sub commify {
my $i = shift;
die "Bad integer $i" unless $i=~/\A-?[0-9]+\z/;
my $in = "$i$i";
my $ptr = $ffi->cast('string' => 'opaque', $in);
c_snprintf_i($ptr, length($in), "%'d", 0+$i);
my $out = $ffi->cast('opaque' => 'string', $ptr);
return $out;
}
print commify(42e6), "\n";
This will print "42,000,000" for an en_US locale and "42.000.000" for a de_DE locale (this is the same behavior as /usr/bin/printf).