use strict;
use warnings;
my $string = 'title: ABC_II';
foreach my $index (qr/I/, qr/II/, qr/III/) {
    print "Match\n" if $string =~ m/ABC_$index/;
}

##</code><code>##

use strict;
use warnings;
my $string = 'title: ABC_II';

my $fixed = qr/ABC_/;
foreach my $index (q(I II III)) {
    print "Match\n" if $string =~ m/$fixed$index/;
}