$filename = @ARGV[0];

##</code><code>##

open (FILE,"$filename") || die "Can't Open $filename: $!\n";

##</code><code>##

use strict;
my $filename = shift;
open(my $fh, '<', $filename) or die "Can't open $filename: $!";
my $text = do { local $/; <$fh> };  # slurping into a string
# do something with $text here