perl regex match line or null

ive got trouble with this regex:

$line1 = "bla <bla> bla F=<> bla <> <gggg> bla lba"
$line2 = "bla <bla> bla F=<somethingineed> bla <> <gggg> bla lba"

How can i match with single regex what is between <> in F=<开发者_如何学Go> or F=<somethingineed> it can be null or some string.

something like this should work, it'll only match stuff following F=

/F=<([^>]*)>/