Repeated match with regex

I wrote parsing for graphviz dot files today and found interesting feature of perl regex engine. It can match a pattern repeatedly to sections of the string.

Small excerpt looks like this.

my $dot_props = 'len=2,font="Arial Black",style=box';
while($dot_props =~ /\G \s* (\w+) \s* = \s* (\w+|".*?") \s* ,? /gcx) {
    print "$1\t$2\n";
}

The string for parsing is defined on first line, there are several key-value pairs separated by comma. Simple split on comma does not work well here, because it can also show up between quotes.

Pieces

One pair can be matched by this regex

/ \s* (\w+) \s* = \s* (\w+|".*?") /x;

For those unfamiliar with the syntax:

Now using global match in a loop we can get one pair after another. The only remaining part is taking in account last comma (optional) and anchor regex to end of previous match with \G.

Conclusion

So the example on the top produces this output

len     2
font    "Arial Black"
style   box