m/^ ( NANQ|INF|NANS| # Possible non numerics \d+ # a number ... (?:[,\.]\d+)? # ... with an optional decimal part ) # memorise the value of : tin . \s+ ( NANQ|INF|NANS| # The same one \d+ (?:[,\.]\d+)? ) # memorise the value of : tout . \s+ (?:[\d\s\.,]|NANQ|INF|NANS)+ # Rest of the line . $/x