"
(?P<prop>[\w-]+) # property name
(?P<prop_params>; # property params, e.g. dstparams
( [\w/,-]+(=[\w/,-]+)?) # first param key[=val] element
(;[\w/,-]+(=[\w/,-]+)?)* # additional key[=val] elements
)?: # colon separator between prop and main params
(?P<params> # main params
( [\w/,-]+(=[\w/,-]+)?) # first param key[=val] element
(;[\w/,-]+(=[\w/,-]+)?)* # additional key[=val] elements
)
"
gmx