Also:

>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
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Update: A small subtlety: The use of the /m regex modifier in the  qr{$_}xms regex in the example above causes the  $ assertion (see Metacharacters) to match before any embedded newline in the string or before the absolute end of the string. If a match only at the absolute end of string is desired, use  \z instead (see Assertions).