#! /usr/bin/perl
open(FILE,"<pmregex.txt");
my @lines=<FILE>;
close(FILE);
print "Class ID\n";
my $found=0;my $id;
foreach my $line(@lines) {
    if($line=~ /ID:/) {
        $id=$';
        chomp($id);
        $found=0;
    }
    if($line=~ /Check./) {
        print "$&";
        if($found==0) {
            print " $id";$found=1;
        }
        print "\n";
    }
}
[download]

output

Class ID
Check1 001
Check2
Check3 002
Check4
[download]

your code seems complex to me so i have written my own
use flag if you want to print a id only once