You are reading the name of the file you wish to process from STDIN but you have not chomped the newline from the string so your open will fail. BTW, it is now recommended to use lexical filehandles and the three argument form of open.

use strict;
use warnings;

my $inputFile = <>;

open my $inputFH, q{<}, $inputFile
   or die qq{open: < $inputFile: $!\n};
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This produces

$ cat spw718152.dat
SNPSTER2_50_3_1_119_588        10
SNPSTER2_50_3_1_121_522        16
SNPSTER2_50_3_1_119_260        27
$ ./spw718152
spw718152.dat
Unsuccessful open on filename containing newline at ./spw718152 line 8
+, <> line 1.
open: < spw718152.dat
: No such file or directory
$
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Adding the chomp will allow the file to open. Using map and taking advantage of the default behaviour of split, which is to operate on $_ splitting on whitespace (including newlines) and discarding empty trailing fields, gives us this.

use strict;
use warnings;

use Data::Dumper;

chomp( my $inputFile = <> );

open my $inputFH, q{<}, $inputFile
   or die qq{open: < $inputFile: $!\n};

my %dataItems =
   map { split }
   <$inputFH>;

close $inputFH
   or die qq{close: < $inputFile: $!\n};

print Data::Dumper->Dumpxs( [ \ %dataItems ], [ q{*dataItems} ] );
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Which produces.

$ ./spw718152
spw718152.dat
%dataItems = (
               'SNPSTER2_50_3_1_121_522' => '16',
               'SNPSTER2_50_3_1_119_588' => '10',
               'SNPSTER2_50_3_1_119_260' => '27'
             );
$
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I hope this is of interest.

Cheers,

JohnGG