Kenosis it was resolved. Im facing another issue. I need to pick list.txt files one by one from each 5 subdirectories(d1,d2,d3,d4,d5) in the present directory. Here's the relevant snippet from the code

#!/usr/bin/perl
use strict;
use warnings;
use List::Util qw/ max /;

open my $fh, "<", 'SUPERLIST_PRODUCT' or die $!;
my $spr_prod = do {local $/; <$fh>};
close $fh or die $!;
my @spr_prod = $spr_prod =~ /\d+/g;

open $fh, "<", 'SUPERLIST_SUBSTRATE' or die $!;
my $spr_substr = do {local $/; <$fh>};
close $fh or die $!;
my @spr_substrate = $spr_substr =~ /\d+/g;

my @matrix;
my $path = '.'; # (current directory - '.') or path to data files
my @file = qw/list.txt/;
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