If your files contain a single line with the array elements separated by commas then you will need to split the line, otherwise @array will contain just a single element ("1,2,3,4") and @array1 will also contain just a single element ("1,5,6,7"). Try reading the files in this way:

use strict;
use warnings;

use Array::Utils qw(:all);

my $file = 'single.txt';
my $file1 = 'single1.txt';
my $fh;

my @array;
open($fh,"<",$file) or die("Could not open $file: $!");
while (my $line = <$fh>) {
    chomp $line;
    next unless $line;
    push(@array, split(',',$line) );
}
close($fh);

my @array1;
open($fh,"<",$file1) or die("Could not open $file1: $!");
while (my $line = <$fh>) {
    chomp $line;
    next unless $line;
    push(@array1, split(',',$line) );
}
close($fh);
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