I needed a way for a user to specify multiple items and to have each item in an array. Basically, 21, 35, 42-45, 19 needs to be expanded to 21, 35, 42, 43, 44, 45, 19 and have each number (seperated by anything matching \s*,\s*) put in an array.

Update Push integers into @expanded instead of strings in the else block. Thanks jeffa!

Update2 Now splits on \s*,\s* (and \s*-\s* for the ranges). Thanks again to jeffa for the suggestion.

Update3 The sub will now correctly deal with reverse ranges (ex/ 42-13) as well as abbreviated ranges (ex/ 123-5 produces 123, 124, 125). 123-35 also works as expected. If you give it 123-19, it will do a reverse abbreviated range : ) producing 123, 122, 121, 120, 119.

Update4 At jeffa's suggestion, I changed my use of the ternary operator so that it is being used to assign a value instead of in void context.

sub expandRanges {
    my @pieces = split /\s*,\s*/, $_[0];
    my @expanded = ();
    
    foreach my $piece (@pieces) {
        next if $piece !~ /\A[\d\-\s]+\z/;

        if ($piece =~ /-/) {
            my @tmp = split /\s*-\s*/, $piece;
            
            my $diff = length($tmp[0]) - length($tmp[1]);
            $tmp[1] = substr($tmp[0], 0, $diff) . $tmp[1] if $diff;
            
            push @expanded, $tmp[0] > $tmp[1]
                ? reverse ($tmp[1]..$tmp[0])
                : ($tmp[0]..$tmp[1])
            ;
        } else {
            push @expanded, int $piece;
        }
    }
    return @expanded;
}

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In reply to Expand Ranges in Lists of Numbers by The Mad Hatter

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