c:\@Work\Perl\monks>perl -wMstrict -le "my @tests = qw[ 10-K 10-KSB 10-K405 10-KSB405 10-Q 10-K/B 10-KSB/ABC 10-K405/A 10-KSB405/A 10-Q/A 10-KA/ ]; ;; my $formget = qr{ (?i) 10- [KQ] [A-Z0-9]* (?! /) }xms; printf 'valid: '; /^$formget/ and printf qq{'$_' } for @tests; print ''; ;; my $formget2 = qr{ (?> (?i) 10- [KQ] [A-Z0-9]*) (?! /) }xms; printf 'valid2: '; /^$formget2/ and printf qq{'$_' } for @tests; " valid: '10-K' '10-KSB' '10-K405' '10-KSB405' '10-Q' '10-KSB/ABC' '10-K405/A' '10-KSB405/A' '10-KA/' valid2: '10-K' '10-KSB' '10-K405' '10-KSB405' '10-Q'