Try the following:

#!/usr/bin/perl
# example blacklisting

@sites = (
    "http://www.rtfm.com", "http://www.alottatax.com",
    "http://www.kingdom.com/cgi-bin/script.pl"
);

@blacklist = ( "cgi", "blabla", "testme" );

foreach $site (@sites) {
    &blacklist();
}

sub blacklist {
    foreach $blacklist (@blacklist) {
        if ( $site =~ m/$blacklist/gi ) {
            print "$site blacklisted - $blacklist\n";
            return; #Change1
        }
        else {
            print "$site ok\n";
            return; #Change2
        }
    }
}
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