http://www.perlmonks.org?node_id=636799


in reply to Programatically detecting a change in letters

how about this approach:

# ASSUME: words are sorted lexically ascending. use warnings; use strict; my $last_anchor = qr{ \z \A }xms; # init to never-matching pattern my $first = qr{ [A-Za-z] }xms; my $anchor = qr{ $first [AEIOUaeiou] }xms; my $letters = qr{ [_A-Za-z] }xms; my $sequence_number_field = qr{ \d+ : [ ]{4} }xms; WORD: while (<DATA>) { next WORD unless m{ $sequence_number_field (?! $last_anchor) # NO match to last anchor ($anchor $letters*) # capture anchoring word to $1 }xms; my $word = $1; $last_anchor = qr{ @{[ substr $word, 0, 2 ]} }xms; print "$word: $_"; } __DATA__ 1: xxAardvark <-- first if really Aardvark 2: Abacus 3: Actuary 4: Additive 5: Aeolian <-- first if no Aardvark 1930: Nails <-- #Na here 1931: Naked 1932: Name 1933: Napkin 1934: Narcotics 1935: Narrow 1936: Nature 1937: Nausea 1938: Navel 1939: Navy 1940: Nazi 1941: Nearsighted <-- #Ne here 1942: Neck 1943: Necklace 1944: Necktie 1945: Necromancer 1946: Need 1947: Needle 1948: Negligee 1949: Neighbour 1950: Neighbourhood 1951: Nephew 1952: Neptune 1953: Nerd 1954: Nervous_Breakdown 1955: Nest 1956: Net 1957: Nettles 1958: New 1962: New_Year 1959: News 1960: Newspaper 1961: Newspaper_Reporter 1963: Nickname <-- #Ni here 1964: Niece 1965: Night 1966: Nightclub 1967: Nightgown 1969: Nightingale 1968: Nightmare 1970: Ninepins 1971: Nipples 1972: Nobility <-- #No here 1973: Noise 1974: Noodles 1975: Noose 1976: North 1977: Northern_Lights 1978: Nose 1979: Notary 1980: Notebook 1981: November 1982: Nuclear_Bomb <-- #Nu here 1984: Numbers 1983: Numbness 1985: Nuns 1986: Nuptial 1987: Nurse 1988: Nursing 1989: Nuts 1990: Nymph