use warnings;
use strict;

while (<DATA>){
    chomp;
    print "$_ matches\n" if /ABC(?!Z)/; 
}

__DATA__
ABC
ABCD
ABCZ
ABCZADF
ABCDZADF
AB
XFC
123
AB1
ABC1
XXXABCZ2
ZZZABCDZ2

__END__
ABC matches
ABCD matches
ABCDZADF matches
ABC1 matches
ZZZABCDZ2 matches