$ cat 11104497.pl
#!usr/bin/local/perl
use strict;
use warnings;

my %count;
my $file_name = shift or die "Usage: perl $0 [FILE]\n";

open my $fh, '<', $file_name or die "Could not open '$file_name' $!";

while ( my $line = <$fh> ) {
    chomp $line;
    foreach my $word ( split /\s+/, $line ) {
        $count{$word}++;
    }
}

foreach my $word ( sort keys %count ) {
    printf "%-31s %s\n", $word, $count{$word};
}

# ..

my @sorted_by_count = sort { $count{$b} <=> $count{$a} } keys %count;

print "These are the 10 most frequented words of $file_name :\n";

print "$_ occured $count{$_} times\n" for @sorted_by_count[ 0 .. 9 ];