As rdfield already mentioned, your problem is in the assignment of open()'s result to your array @r.

When reading the file's content, remember that Perl doesn't remove the linebreaks automatically; that's up to you (use chomp() for that):

# ...
@r = <DATFH>;
chomp @r;
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#!/usr/bin/perl
use strict;
use warnings;

my $file = 'data.txt';

open my $datfh, '<', $file or die "$file: open(ro) failed: $!\n";

while ( my $line = <$datfh> ) {
  chomp $line;
  my @fields = split /\|/, $line;
  # work with your data fields
}

close $datfh or die "$file: close(ro) failed: $!\n";
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update: paragraph tags and text added;
update2: typo fixed; thanks johngg