Welcome to Perl and to programming!.

To solve this problem Hash comes to mind. The code below open a new file to be read into i.e "freq_file.txt", and a file to read from. Print in the new file the values matched and it's frequency. See below:

#!/usr/bin/perl
use warnings;
use strict;

print "Enter the name of your file, ie myfile.txt: ",;
chomp( my $file = <STDIN> );
my %found;

open my $fh,  '>', 'freq_file.txt' or die "can't open this file: $!";
open my $fh2, '<', $file           or die "can't open this file: $!";
while ( my $line = <$fh2> ) {
    $found{$_}++ foreach split /\s+?/, $line;
}
print $fh "Frequence\tValue Found", $/;
print $fh $_, "\t\t", $found{$_}, $/ foreach sort keys %found;

close $fh2 or die "can't close file: $!";
close $fh  or die "can't close file: $!";
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I hope this helps