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;
Instead of reading the complete file into an array (and into the memory) you can read linewise:
#!/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";
update: paragraph tags and text added;
update2: typo fixed; thanks johngg