use strict;
use warnings;
use Regexp::Assemble;

my %hash_table = (12345 => 1, 8976 => 2, 1046 => 3);
my $assemble = Regexp::Assemble->new (flags => 'i');

$assemble->add (keys %hash_table);

my $match = $assemble->re ();

while (<DATA>) {
    chomp;

    my ($objid, $other) = split;

    if ($objid =~ /($match)/) {
        print "$1 is present in $objid\n";
    }

}

__DATA__
012345998 line matches
000104600 line matches
012389710 line doesn't match