qr[
    ^\s*                       ## from the start of the string, skip whitespace (if any)  
    (?: \d+ - \d+ )            ## then grab (at least one) pair of numbers separated by '-'
    (?:                        ## a group 
         \s* , \s*                 ### a comma, optionally preceded or followed by whitespace
         \d+ - \d+                 ### and another pair of numbers separated by '-'
    )*                         ## zero or more times
    \s*$                       ## to the end of string, optionally skipping whitespace if any
]x