[SOLVED] Capture one suffix containing known substring when multiple matching prefixes (without known substring) found

Capture one suffix containing known substring when multiple matching prefixes (without known substring) found

Given an input of multiple string, some containing the prefix is:, I need to capture one instance of the substring "Foo" or "Bar" following the is: prefix regardless of how many times is:Foo/is:Bar or is:Baz/is:Xyzzy appear.

Using the following regex: .*is:\b([Foo|Bar]*)\b.*

And using the following examples of test input lines with matches:

"is:Baz is:Foo FooBar"          # Captures "Foo"
"is:Foo FooBar is:Bar"          # Captures "Bar"
"is:Bar FooBar FooBaz Baz"      # Captures "Bar"
"FooBar is:Bar FooBaz"          # Captures "Bar"
"FooBar is:Xyzzy is:Foo"        # Captures "Foo
"is:Baz FooBar is:Foo"          # Captures "Foo"
"FooBar is:Foo is:Xyzzy"        # No capture

In the final line I want to also capture is:Foo, but the capture is thrown off by is:Xyzzy. This isn't an exhaustive list of possible test cases but it illustrates to problem I'm coming up against.

Solution

You can write the pattern using a grouping without the [ and ] that denotes a character class.

You don't need a word boundary here :\b as it is implicit due to the following alternation of (Foo|Bar)

You can append a word boundary before \bis

.*\bis:(Foo|Bar)\b.*

See a regex101 demo.