Have you checked what's in %loco_data?

use strict;
use Data::Dump qw/dump/;
my %loco_data = <DATA>;
print dump \%loco_data;
__DATA__
123
234
345
456

#{
#  "123\n" => 234
#             ,
#  "345\n" => 456
#             ,
#}
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Also, you should at least use strict;; use warnings; and use diagnostics; will give you even more info.
For opening files it's better to use the 3-element open.
Is the code you posted a cut-n-paste? I don't see where $locodn is coming from, or why you'd need to chop it.
chomp is generally preferable to chop.
To increment variables: $linecnt1++ or $linecnt1 += $x.