As well as the issues with the success of the open and with chomp already pointed out by jwkrahn, you should note that the ($_[0] => $_[1]) is superfluous and could be omitted to get the same result.

my %result = map {split /\|/} <FILE>;
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Using a lexical filehandle inside the scope of a do would save an explicit close.

use strict;
use warnings;

use Data::Dumper;

my $inFile = q{spw708412.dat};
my %stuff  = do
   {
       open my $inFH, q{<}, $inFile
          or die qq{open: < $inFile: $!\n};
       map { chomp; split m{\|} } <$inFH>;
   };

print Data::Dumper->Dumpxs( [ \ %stuff ], [ q{*stuff} ] );
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Running it.

[johngg@ovs276 perl]$ cat spw708412.dat 
abc|123
def|456
[johngg@ovs276 perl]$ ./spw708412
%stuff = (
           'def' => '456',
           'abc' => '123'
         );
[johngg@ovs276 perl]$
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I hope this is of interest.

Cheers,

JohnGG