>perl -wMstrict -le
"my ($patterns) =
   map qr{$_}xms,
   join ' | ',
   qw(catalina\.properties \.key$ tomcat-users\.xml)
   ;
 ;;
 print $patterns;
 ;;
 my $string = 'foo.key';
 print 'match' if $string =~ $patterns;
"
(?msx-i:catalina\.properties | \.key$ | tomcat-users\.xml)
match