nick 5
nick 10

##</code><code>##

^[a-z]+\t\d+$

##</code><code>##

use strict;
use warnings;

my $fname = shift or die "usage: $0 file\n";
open( my $fh, '<', $fname ) or die "error: open '$fname': $!";
my $lcnt = 0;
my $line;
while ( defined($line = <$fh>) ) {
   ++$lcnt;
   chomp $line;
   $line =~ /^\s+/ and die "error: line $. contains leading  whitespace\n";
   $line =~ /\s+$/ and die "error: line $. contains trailing whitespace\n";
   length($line) or die "error: line $. is empty\n";
   $line =~ /^[a-z]+\t\d+$/ or die "error: line $. ($line) does not match word TAB number\n";
}
close $fh;
warn "file '$fname': $lcnt lines, no data format errors detected\n";

##</code><code>##

error: line 1 contains trailing whitespace