param('s1') =~ m/ad/i

##</code><code>##

param('s1') =~ /a/i and param('s1') =~ /d/i 

##</code><code>##

param('s1') =~ /a/i or param('s1') =~ /d/i

##</code><code>##

my @list = qw(a b c);
if (param('s1) =~ /[@list]/xi) {
    print "one of the characters matched"
}