c:\@Work\Perl\monks>perl -wMstrict -le
"chomp(my $string_to_find = <STDIN>);
 ;;
 my @array_to_search = qw(Foo whathi$denever Bar 12hi$den456);
 ;;
 my $rx_search = qr{ (?<= \d) \Q$string_to_find\E (?= \d) }xms;
 ;;
 for my $s (@array_to_search) {
   print qq{'$s' has '$string_to_find'} if $s =~ $rx_search;
   }
"
hi$den
'12hi$den456' has 'hi$den'