There are many ways. Start here: How do I post a question effectively?

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

my $predetermined = 6;

my @nums = qw(6 645 1086 1996 2015 2026);

for my $num (@nums){
    if ($num =~ /$predetermined$/){
        print "$num\n";
    }
}
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-stevieb