#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

my $file = 'file1.txt';
open (my $in,  "<", $file)
    or die "Can't open $file: $!";

while (<$in>) {     # assigns each line in turn to $_
    chomp;
    next if /^\s*$/; # skip blank lines
    say "Line number: " . $. . " Content of line: " . $_;    # print contents of $_ line by line
}

close $in
    or warn "Can't close $file: $!";

__END__

$ perl test.pl
Line number: 1 Content of line: ABS0056
Line number: 3 Content of line: ABS0057
Line number: 5 Content of line: ABS0058
Line number: 7 Content of line: ABS0059