find_repeating_defs.pl

use warnings;
use strict;
# http://search.cpan.org/~zmij/Array-Utils-0.5/Utils.pm
use Array::Utils qw(:all);

# $/ is the input record separator
# local is because it's a global variable
local $/ = undef;
open(DATA, "<", $ARGV[0]) or die;

my $file_data = <DATA>;

# g if trying to globally match the pattern repeatedly
my @all_defs = ($file_data =~ /PREPROC_ADD_MACRO\(info,(.*?)\)/g );
my @uniq_defs = unique(@all_defs);

# Find symmetric difference
my @repeat_defs = array_diff(@all_defs, @uniq_defs);
print join( "\n" , @repeat_defs)."\n";

# Output of the script
# __INT32_MAX__
# __INT64_MAX__
# __INT8_MAX__
# __INT_FAST16_MAX__
# __INT_FAST16_TYPE__
# __INT_FAST8_MAX__
# __UINT16_MAX__