#!/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

##</code><code>##

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

my %hash;
# reset line numbering on each input file
while (<>) {
    chomp;
    next if /^\s*$/; # skip blank lines
    say "$.\t$_";
    $hash{$ARGV}{$.} = $_;
} continue {
    close ARGV if eof;  # Not eof()!
}

print Dumper \%hash;

__END__

$ perl test.pl file1.txt file2.txt
1	ABS0056
3	ABS0057
5	ABS0058
7	ABS0059
1	ABS0060
3	ABS0061
5	ABS0062
7	ABS0036
$VAR1 = {
          'file2.txt' => {
                           '7' => 'ABS0036',
                           '5' => 'ABS0062',
                           '1' => 'ABS0060',
                           '3' => 'ABS0061'
                         },
          'file1.txt' => {
                           '5' => 'ABS0058',
                           '7' => 'ABS0059',
                           '1' => 'ABS0056',
                           '3' => 'ABS0057'
                         }
        };

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use IO::All -utf8; # Turn on utf8 for all io

my @lines = io('file.txt')->chomp->slurp;      # Chomp as you slurp

print Dumper \@lines;

__END__

$ perl test.pl
$VAR1 = [
          'line 1',
          'line 2',
          'line 3',
          'line 4'
        ];